PURPOSE OF REVIEW: Update recent advancements regarding the effect of high-animal protein intakes on calcium utilization and bone health.

RECENT FINDINGS: Increased potential renal acid load resulting from a high protein (intake above the current Recommended Dietary Allowance of 0.8 g protein/kg body weight) intake has been closely associated with increased urinary calcium excretion. However, recent findings do not support the assumption that bone is lost to provide the extra calcium found in urine. Neither whole body calcium balance nor bone status indicators, negatively affected by the increased acid load. Contrary to the supposed detrimental effect of protein, the majority of epidemiological studies have shown that long-term high-protein intake increases bone mineral density and reduces bone fracture incidence. The beneficial effects of protein such as increasing intestinal calcium absorption and circulating IGF-I whereas lowering serum parathyroid hormone sufficiently offset any negative effects of the acid load of protein on bone health.

SUMMARY: On the basis of recent findings, consuming protein (including that from meat) higher than current Recommended Dietary Allowance for protein is beneficial to calcium utilization and bone health, especially in the elderly. A high-protein diet with adequate calcium and fruits and vegetables is important for bone health and osteoporosis prevention.

Background

For decades now, it’s often been thought, felt or claimed that a high dietary protein intake had a detrimental effect on calcium metabolism and bone health; certainly many groups promoting low-protein dietary approaches tend to echo/parrot this idea.

This idea came around in the mid-20th century but was based on some, shall we say, questionable research.  In it, totally purified proteins were given (that is, no other nutrients were present) and a loss of calcium in the body (in the urine) was documented.  It was simply assumed that this had a negative impact on bone health.

Despite later research showing that it was much more complicated than this (i.e. that proteins containing other nutrients had different effects and that other parts of the diet played a major role in the overall effect), this idea is simply repeated as if it were still unquestionably true.  I dealt with this issue to some degree in The Protein Book, in a chapter called Protein Controversies, which is reproduced here on the main site.

As well, there has long been a secondary data set (seemingly ignored by anti-protein folks) showing that higher protein diets actually IMPROVE bone healing following things such as breaks or fractures.  Clearly the idea that ‘protein is bad for bone’ is a bit more complicated than just a soundbite.  The review paper I want to look at today examines the topic in some detail.

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The Paper

The paper begins by pointing out that bone is over 50% protein to begin with and that there has long been concern that the modern Western diet is detrimental to bone health due to the production of acids within the body.  This is something I imagine readers have at least seen mentioned in recent years (I get the occasional question about it) with some going so far as to claim that the body’s pH is THE KEY to all health (some even claim that a drop in cellular pH is the cause of cancer).

While it’s not quite that cut and dry, clearly the modern Western diet tends to promote the production of metabolic acids and at least some degree of metabolic acidosis.  This is due to a number of factors including a high protein intake (proteins are acid promoting), insufficient fruit and vegetable intake (both of which are net base producing for the most part), along with other factors such as sodium and potassium balance (excessive sodium intake relative to potassium can increase the acid load of the body).  You can find long lists of foods online in terms of their net acid or base producing potential.

And certainly, as discussed briefly in Protein Controversies, acidosis can cause problems in the body.  It’s relevant to today’s paper in that the body appears to buffer this acid load by releasing calcium, presumably from bone.  In that current research is suggesting that the RDA for protein is actually too low for some populations (notably older individuals) and with the current interest in high-protein diets for weight/fat loss and maintenance, it’s important to know whether or not these dietary approaches are having negative impacts on bone health.

The paper looks in some detail at the issue of acid/base balance and calcium metabolism. As noted above, the generation of metabolic acids causes a number of effects in the body, all of which could potentially impact negatively on calcium metabolism and bone health.  As well, studies clearly show both that:

1. The generation of metabolic acids causes increased calcium loss in the urine
2. Counteracting acidosis with base-forming minerals (e.g. potassium bicarbonate) decreases calcium excretion

While the above is clear, the direct impact of dietary protein on bone health is a bit less clear with the results of more direct epidemiological data showing mixed results in terms of the actual impact on bone health.  As well, citing a review by Fenton, the paper points out that:

…neither calcium balance nor the bone resorption marker, N-telopeptides, was affected by diet-induced changes in net renal acid excretion despite a significant linear relationship between an increase in renal net acid excretion and urinary calcium.

That is, while it’s clear that increased dietary acid load causes increased urinary calcium excretion, it’s less clear if this has any real direct impact on the body’s net calcium balance or overall bone health.

Moving on to more direct effects, the paper looks at the very old data (using primarily purified proteins) showing that for every increase in dietary protein by 1 gram, there was a 1 mg increase in urinary calcium loss (raising the question of why not simply scale calcium intake to protein intake to offset this); this led to the assumption that bone health was being compromised.

However, in direct contrast to this, the majority of epidemiological studies find that a higher protein intake is associated with increased bone mineral density with only a few finding a negative impact.  As well, while weight loss per se tends to cause a decline in bone health, some research has found that high-protein weight loss diets reduce the loss of bone mineral content; that is, high-protein intakes on a diet are beneficial.

The primary acid formation from protein comes from the sulfur containing amino acids (cysteine and methionine) and these are found in higher amounts in animal vs. vegetable proteins; it’s often been assumed that a higher vegetable protein intake would therefore have less of an impact on bone health.

However, this also turns out to be incorrect; the paper points out that studies of high-meat protein intakes either show no overall effect on net calcium balance and a higher animal protein intake is actually associated with increased bone mineral density; as well studies show a negative association between vegetable protein and bone mineral density.

It’s worth noting that strength/power athletes, who have traditionally consumed a high-protein diet are typically found to have higher bone densities compared to sedentary individuals.  As the paper points out:

Changes in bone mass, muscle mass and strength track together; thus maintenance or an increase in muscle mass and function maintains or enhances bone strength and mineral density.

And while the increase in urinary calcium excretion with increasing protein cannot be simply ignored, current data suggest that this isn’t actually due to a loss of bone mass.  Rather, increased protein intake leads to increased calcium absorption from the gut; the loss in the urine is simply due to more calcium being absorbed.   The increased loss is simply due to more being absorbed from the diet; interestingly, this effect is more pronounced when calcium intake is low to begin with.

In terms of mechanism, higher protein intakes raise levels of the hormone IGF-1, which stimulates bone formation; this probably explains the benefits of a high-protein intake on bone healing.  As well, high protein intakes have been shown to decrease levels of parathyroid hormone (PTH), a hormone that is involved in the loss of bone mass.  Low protein intakes are associated with increased PTH and lowered bone mineral density.

Finally, as I mentioned in the introduction, you can’t simply look at protein intake outside of the rest of the diet and there are clear interactions with other nutrients.  I mentioned above that protein intake interacts with calcium intake, increased absorption.  As well, a high protein intake has been shown to increase bone health in older individuals when calcium and Vitamin D are supplemented.  Finally, ensuring a sufficient intake of fruits and vegetables (which neutralize the acid load of protein) should help to ensure the impact of dietary protein on bone health is positive rather than negative.

Summing up, the researchers conclude thus:

Although a high meat or protein intake increases renal acid load and urinary calcium excretion, recent findings do not support the claim that bone is the source of the extra calcium lost in the urine.  In addition, evidence is lacking that shows high-protein intakes, including that from animal sources, affect whole body calcium balance or contribute to osteoporosis development and fracture risk.

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Summing Up

I don’t have a whole lot to add to the above conclusion.  Clearly the negative impact of dietary protein on bone health would appear to be overstated to some degree. Under certain circumstances (low calcium/Vitamin D intake, insufficient intake of fruits and vegetables), it’s certainly possible that a high-protein intake could have negative impacts.  But again this comes down to an issue of context.   And in the context of sufficient net acid neutralizing foods (fruits, vegetables, sufficient potassium intake) along with sufficient calcium/Vitamin D intake, the impact of protein on bone health would appear to be positive overall.

Question: I suppose a follow-up question to this answer is just how rare it would be to cross a true “point of no return” where you may have fouled up your internal physiology to where it may never be able to rebound. Or is it usually a case of time and reversing some of the actions that cause it in the first place? i.e. the longer and more extreme the descent, the longer it will take to recover, but recovery is entirely possible

Would clinically severe eating disorders probably be the only instances where someone could allow things to devolve to such a degree that any sort of irreparable damage may have been done to some part of the body and its normal functioning?

Answer: First let me say that I am not and do not claim to be any sort of expert on the topic of eating disorders.  It’s simply not been a major area of interest of mine.  I think it’s worth considering that what is going on in something like anorexia or bulimia is quite different than what is going on with the topic I was primarily addressing in the original Q&A, to wit contest diets in bodybuilders/physique athletes.

For example, if nothing else we can see massive differences in the nutritional intake of a dieting bodybuilder/physique competitor (typically based around high protein intakes and ‘healthy’ foods) as opposed to the near complete absence of food in the anorexic or the alternation of binging and purging in the bulimic.

With that said, what little literature I have looked at in terms of recovery from eating disorders doesn’t lead me to believe that there is any sort of permanent damage.  So long as a ‘normal’ weight is regained (here we’re typically looking at the anorexic), things come more or less back to normal.  Even in the seminal Minnesota study, metabolic rate eventually rebounded to normal; of course the subjects had regained all of the fat they had lost as well for that to occur.

But again, this is really outside of my major sphere of interest; if anyone reading this has expertise that can contribute to this question, I think we’d all love to see it.

Question: Layne Norton once said that from the day one begins to eat normally again, it can take anywhere from 3-4 months to completely restore BMR to 100% from post-dieting levels. Although he didn’t cite it, do you know of any studies roughly reflecting this extended time frame? I’m only referring to restoration of normal hormone output and, thus, adaptive thermogenesis, since if the weight loss were maintained, BMR would still be relatively lower than it was pre-diet simply by virtue of a lower final body weight.

Answer: No direct research on this comes to mind immediately although it may exist. I think the problem is that, usually in looking at post-diet ‘recovery’ there is almost always a regain in body fat which tends to color the issue.  For example, in the Minnesota study that I mentioned in the question above, following the 6 months of semi-starvation, the men were allowed to eat as much as they wanted.  And they went nuts, eating massive numbers of calories and regaining fat.  Which normalized metabolic rate eventually but doesn’t really apply to what you seem to be describing.

Frankly, I’m not 100% sure that hormones will ever return to completely normal (see next question) assuming that the lowered body weight/body fat level is maintained. They can be improved by raising calories to maintenance for sure.  This is part of the rationale behind The Full Diet Break although that’s really meant to break up periods of explicit dieting (I also suggest it at the end a diet to start normalizing things).  Which is a long way of saying “I don’t know”  If Layne has a reference for that, I’d love to see it.

Question: So there is evidence of metabolic derangement, but do you think it is permanent even when returning to normal caloric intake?

Answer: The studies of the post-obese (see next question) suggest that, even at weight maintenance (i.e. when calories have been returned to normal), there is still a small overall reduction in basal metabolic rate (on the order of perhaps 5%) compared to someone who is ‘naturally’ of that weight.  Meaning that if you compare someone who is 180 pounds without dieting to someone who has dieted down to 180 pounds, the second person will show a slightly reduced metabolic rate compared to the predicted values.  But the effect is slight when calories are brought back to maintenance.

As I discussed in the original Q&A, it looks like the main impact in terms of reducing daily energy expenditure is on spontaneous activity levels; this probably explains why exercise seems to have so much bigger of an impact on weight maintenance than weight loss (as I discussed in Exercise and Weight/Fat Loss Part 2).

I am unaware of any research examining if this is maintained in the long-term (i.e. will the post-obese continue to show decreases in spontaneous activity).  However, the long-term studies of the post-obese (ranging from 2-5 years if my memory serves correctly) suggest that the effect on basal metabolic rate never goes away.  So yes, it’s effectively permanent; it’s simply small.

Question: I’m also wondering about the permanence of any such metabolic adaptations. It seems likely to me that metabolism would return to normal at some point. If so, how long would it take? It seems like I read something about this in a discussion of the Minnesota study, but I’d have to go searching to see if I’m remembering correctly.

Answer: As noted in the question above, what data I’ve seen looking at the post-obese in the long-term suggest that there is a slight reduction in basal metabolic rate that doesn’t appear to ever go away.  At least not in any practical time frame.  Based on what we know about the issue of setpoint (discussed in Set Points, Settling Points and Bodyweight Regulation Part 1) I wouldn’t expect this to ever truly go away.   I imagine someone will ask the logical followup to this in the comments which is “So what about people who get and stay lean in the long-term, how do they do it?”  Maybe addressing that will get me past my writer’s block to write an actual article about it.

Question: I am a clinical nutritionist at clinic where we see a lot of people with “screwed up metabolisms”. In a different vein, there are the people who got fat from overeating and eating the wrong types of foods and became insulin resistant. Now they have to eat low calorie diets otherwise they gain weight.

One of my clients weighs 360 lbs and her BMR according to the the InBody is 2700 calories. The girl eats maybe 1200 calories a day and maintains that weight. Reversing insulin resistance by eating the proper foods and incorporating resistance training obviously helps. I am wondering if there is an approach to increasing calories systematically when working to reverse insulin resistance without gaining weight?

Answer: This is really a bit outside of what the original Q&A was discussing but I’ll address it anyhow; certainly there can be metabolic derangements that occur in obesity (what’s cause and what’s effect is often hard to determine).  However, it’s highly unlikely that your client is truly maintaining her weight on 1200 calories per day if her measured BMR is that high (meaning that her total daily energy expenditure is even higher); insulin resistance or not, that’s simply a physiological impossibility.

The more likely (and exceedingly common) issue is that she’s simply consuming more food than she’s aware of or self-reporting.  Because even in studies of insulin resistance, when calories are reduced (and and accurately monitored), weight/fat loss occurs.  So either she’s a physiological anomaly or she’s not really eating 1200 calories per day.  And my experience (along with a large body of research) suggests that it’s the latter issue that’s the cause of the problem.

Thanks for the questions folks!

I would be surprised if most on the Internet or who were involved in training and nutrition weren’t familiar with the name Tom Venuto.   I’ve known Tom (via email correspondence anyhow) for over a decade and he’s always been one of the good guys in the field.  I may not always agree with him, but I’ll always listen to what he has to say.

For those who have been living under a rock and have managed to avoid hearing about him, Tom is not only a successful natural bodybuilder, he is the author of perhaps one of the best books ever written about fat loss which is Burn the Fat, Feed the Muscle.

In a field where most of the information ranges from bad to downright awful, Burn the Fat, Feed the Muscle stands out as being filled with excellent information on the how-to’s of shedding fat.

From diet to training to everything in-between, it’s all covered and all quality information (even if a few bits of the information are a bit out of date/incorrect; such as the old saw that eating many small meals stokes the metabolism).

Tom is also the author of a book that I’ve been meaning to review for months called The Body Fat Solution which deals more with behavioral issues related to losing fat and keeping it off.  Also, a highly recommended read.

But today I want to talk about Tom’s new product/project which he’s given the (somewhat gag inducing) title of The Holy Grail Body Transformation Program. By ‘holy grail’, as you can see in the subtitle on the cover graphic above, Tom is referring to that commonly desired goal of gaining muscle and losing fat at the same time.

This is a goal that many seek and few attain; usually trying to do both things at once tends to lead most people to spin their wheels.  But as much as anything, this has to do with how they approach the goal.  There are also some issues involved with expectations about what is realistic.  I’ve discussed this issue in some detail in Adding Muscle While Losing Fat – Q&A and won’t rehash that here.  On to the review.

Beginning first with science and theory, Tom looks at some of the basic issues surrounding the topic of gaining muscle while losing fat and why, in a fundamental sort of way, the two goals are antithetical (Tom also examines exceptions, pretty much the same ones I’ve talked about before).  Anyone who has read my own Ultimate Diet 2.0 or the articles Calorie Partitioning Part 1 and Calorie Partitioning Part 2 here on the site will be familiar with this information.  Tom doesn’t spend endless time on this information but covers it thoroughly enough to be clear.

The meat of the book is of course the diet approach and if you’ve already guessed that it’s a cyclical dieting program, you guessed right.  Because fundamentally, outside of the exceptions such as overweight beginners or folks returning from a layoff (or drugs), alternating caloric deficits and surpluses is really the only meaningful way to achieve the goal of simultaneous fat loss and muscle gain since they require distinct nutritional, hormonal and physiological states.

Tom looks at the issue from a rather large scale (e.g. yearly alternation of longer term bulking and dieting phases) to weekly to daily variations in caloric intake; I imagine that well-read, err, readers of my site will be familiar with many of the concepts he’s talking about.

Tom does a thorough job of examining a variety of different strategies (both in terms of the number of dieting days and number of feeding days) ranging from 3:2-3 (3 days dieting, 2-3 days overfeeding) to 3:1 to floating carb days.  As well, daily variation in carb/caloric intake is examined based on the time training is performed.  Essentially what Tom has done is to gather a variety of different strategies (depending on the specifics of the goal) that have been used and looked at them all at once.  I’d note that primarily carbohydrate intake is being modified here so, in essence, the caloric cycling ideas are really carb cycling ideas.

I would note one thing here: the topic of intermittent fasting (IF’ing) is NOT discussed.  I guess we’ll have to keep waiting for Martin Berkhan’s long-awaited book to see this treated in the way it deserved to be.  Neither is the concept of Every Other Day (EOD) refeeds that gets talked about on the support forum from time to time.

Next Tom moves to the discussion of training with, as you might imagine, most of the focus on resistance training (since this is the key to a lot of good things that are desired when the goal is body recomposition).  He doesn’t go into a tremendous number of details here and there are no sample workouts in the main part of the book.

I’d note that one of the appendices does have a sample workout under the name of The New Bodybuilding, basically a 3-4 day/week combination of heavy strength and hypertrophy work; the focus is primarily on more or less general guidelines for proper resistance training.  Tom also addresses the issue of metabolic work and gives different guidelines (primarily for lower intensity cardio) in terms of frequency and duration depending on the specific goal.

Which brings me to my biggest criticism of Tom’s book: there is little attention given to how to ideally integrate the training ideas with the dietary strategies that are outlined (outside of one short comment in the diet section on floating carb days and placing them around important workouts).  Simply, achieving the ‘holy grail’ goal works better when training and diet are integrated properly.

The book rounds itself out with a brief section on lifestyle factors and several appendices that include meal plans, a primer on determining energy requirements and a food database.  I should mention that there is a throwaway ‘bonus’ on the topic of within-day energy balance; essentially an interview with sports nutritionist Dr. Dan Bernadot espousing the idea that large scale swings in caloric intake during the day have negative impacts on body composition.

I say throwaway because it doesn’t say much; as well I think the ideas presented have been amply disproven by the success of people following IF’ing type approaches where very large scale swings in caloric intake are having, if anything, positive benefits when integrated properly with training.

Summing Up: Is The Holy Grail Body Transformation Program great?  I’d have to say no.  It certainly doesn’t live up to the standard set by Burn the Fat, Feed the Muscle and the lack of integration of the training and diet may leave some people confused about how best to approach their goal.  But it does provide a reasonably comprehensive examination of how to cycle calories and carbs to try to achieve the ultimate goal of body recomposition.  Until Martin finally finishes his IF’ing book, Tom’s new book certainly provides a decent look at the topic.  Finally, at $29, the price is certainly reasonable (as such things go).

This sounds like bro-hype but I’m wondering: Is there any truth to this phenomenon?

Answer: This seemed a good followup Q&A after last Friday’s Lean Body Mass Maintenance and Metabolic Rate Slowdown – Q&A since it’s semi-related and I seem to have total writer’s block regarding anything approximating a feature article right now.

There are several issues at stake here and I’m going to address them in reverse order.  Certainly I have seen some weirdness occur (and there is at least one study to support this) where excessive cardio in the face of a large caloric deficit can cause problems, not the least of which is stalled fat/weight loss.  In that study, the combination of a very large deficit plus about 6 hours of cardio seemed to decrease metabolic rate more than the diet alone. This is something I intend to cover in more detail at a later date.

This, along with personal observations, was what led me to strongly suggest against doing a lot of cardio on The Rapid Fat Loss Handbook program; in fact I’d say that a majority of failures on that program can be tracked to people trying to do too much cardio and it doing more harm than good.   Invariably, the folks who minimize activity (beyond the basic weight workouts) and let the deficit of the diet do the work do better in terms of fat loss.  So certainly there is an element of truth to that.

However, we need to look at magnitudes here and do a bit of reality checking. Several in fact.

The first is to look at the food intake.  700-900 calories is not a lot of food and, typically, at the end of a contest diet, hunger is simply off the map.  I find it doubtful that someone is truly consuming that little food on a day to day basis at the end of a contest diet.

Note that I did not say impossible (anorexics certainly seem to do this); I’m simply doubtful that someone is consuming that little food in the face of extreme hunger on a day to day basis.  They may be reporting that that is their true food intake but I’d be doubtful that it was truly that low on an everyday basis.

Now, as discussed in the Q&A I linked above (as well as in other articles on the site and in my books), there is no doubt that the body undergoes a variety of rather annoying adaptations to reduced calories and fat loss.  Reduced metabolic rate, reduced spontaneous activity, etc. all occur and this works to slow fat loss.  But what we’re really dealing with here is a magnitude issue.

First and foremost, if someone is claiming to get fat on only 900 calories per day, that implies that their actual total daily energy expenditure is actually LESS than that. That is, as I discuss in some detail in The Energy Balance Equation, we know that to actively gain fat requires a caloric surplus (relative to expenditure).

To gain fat at say 900 calories, and to do so at any fast rate would imply that daily energy expenditure was significantly less than that.  For example, assume that someone eating only 900 calories per day were gaining fat at a rate of 1 pound per week.  That would imply a 500 cal/day surplus or a total daily energy expenditure of 400 calories per day.

For an average sized male who started out with a maintenance energy expenditure of 2700 calories per day that would be an 85% reduction.  For an smaller female who started with perhaps a 1700 calorie/day maintenance, that would be a 75% reduction from where they started.  And simply, that level of reduction is far and beyond everything that’s ever been measured in the history of research on this topic.

Now, some might argue that the stressors of competition dieting haven’t been examined and they’d probably be right; to my knowledge, no-one has examined the metabolic rate of a bodybuilder following an extreme contest diet.  Quite in fact, most studies don’t examine lean individuals at all but there is one study that is possibly relevant which is the seminal Minnesota Semi-Starvation Study.

I’ve talked about this study before and it represents one of the most massively well-controlled studies on the topic ever done (or that will ever be done).  In it, war objectors were placed on approximately a 50% reduction from maintenance calories (which only put them around 1500 calories/day or thereabouts in the first place) and were held there for 6 straight months.  Activity (walking) was enforced and most men reached the lower limits of body fat percentage by the end of it.  I’d note that only men were studied so it’s possible that women, who are prone to showing more resistance to fat loss, could show a differential response.

And the total reduction in daily energy expenditure only amounted to 40% (of which the majority of that was due to the weight loss).  Weight and fat loss had basically stopped at the end of the study which makes sense; the original 50% deficit had been reduced to at most 10% due to the 40% reduction in metabolic rate.

The bottom line is that no study I’ve ever seen has suggested that total daily energy expenditure could be reduced to the levels that are implied by ‘gaining fat rapidly at 700-900 calories/day’.

So what’s going on?  Certainly some bad hormonal things go on when you combine heavy activity with heavy deficits for extended periods to low body fat levels (I’d note that various types of cylical dieting such as my own Ultimate Diet 2.0 and Martin Berkhan’s Intermittent Fasting approach seem to side-step at least some of this).   Thyroid levels drops, nervous system output drops, testosterone levels crater, cortisol goes through the roof.

And I would suspect/suggest that it is this last effect that is being observed and taken as evidence of ‘metabolic damage’.  In a water depleted, glycogen depleted bodybuilder coming out of a contest diet, water balance is going to go absolutely crazy and cortisol is one mediator of this.  Water retention secondary to glycogen storage will also contribute.

So you have a situation where a post-contest bodybuilder may be seeing just massive swings in water weight (which can appear like rapid fat gain) following the contest; especially when you consider the normal runaway hunger that tends to occur at that point.

Between glycogen storage and simple cortisol mediated water retention, I can’t see any other reason to explain the observation.  Even one day of overeating carbs can cause massive water retention (for example, shifts in water weight of 7-10 pounds over a day or two are not uncommon on cyclical diets) and I suspect that’s what is being observed.

Which is all a long way of saying the following: certainly there is evidence of metabolic derangement when you diet people down to low levels of body fat, this can probably be made worse if you undergo the normal severe overtraining cycle that most dieters go through at that point.  But I don’t see any physiological way that true rapid FAT gain can occur at such low calorie levels.  I’d suspect that water retention (and a bit of neurosis equating water weight gain with true fat gain) is the primary culprit here.

Is this a faulty assumption? I’ve read on many a website that the body goes into “starvation mode”, however that argument doesn’t sit well with me. Either the body requires X amount of energy to function, or it doesn’t. I think “starvation mode” might simply be reduced activity in general, so for a relatively insane individual (read:athlete) who is willing to push hard on a restrictive diet, metabolic slowdown shouldn’t be an issue?

Answer: I suspect that some of this comes down to an issue of semantics (you sort of get to part of what I’m going to talk about in your second paragraph) but some of it doesn’t.  The short answer to your question is that your assumption isn’t entirely correct; even with 100% maintenance of lean body mass (LBM) there can still be some metabolic slowdown.  Now here’s the longer answer.

First and foremost, we need to define some terms and what’s meant by metabolic rate since I suspect that’s part of where some of the confusion is coming from.  On a daily basis, an individual’s total daily energy expenditure is given by three components, which I’ve discussed in detail in Metabolic Rate Overview. They are

1. Resting/Basal Metabolic Rate (RMR/BMR; what I suspect you’re referring to above)
2. Thermic Effect of Food (TEF)
3. Thermic Effect of Activity (TEA)

Where TEA has now been divided into two distinct components: the thermic effect of exercise and non-exercise activity thermogenesis (NEAT).  The distinction being that the first is calories burned during formal exercise and the second, NEAT, is the calories burned during activities such as daily moving around, fidgeting, moving from sitting to standing, etc.  I discussed the potentially major impact of NEAT in a recent research review on Role of Nonexercise Activity Thermogenesis in Resistance to Fat Gain in Humans.

Now, each of the above is determined by various factors including body composition, diet, etc.  And all of them are affected by dieting and the loss of body mass.  Studies have repeatedly shown that individuals who have been dieted down to a given weight will have a lower than predicted metabolic rate compared to someone who didn’t diet to that weight.  That is, someone who ‘naturally’ weighs 200 pounds will have a higher total energy expenditure than someone who dieted down to 200 pounds.

So what’s causing this reduction in total energy expenditure.  A majority of the ‘metabolic slowdown’ that occurs is due simply to the loss of body mass.  Because larger bodies burn more calories (both at rest and during activities) and smaller bodies burn less.

But that’s not the only cause of metabolic slowdown here.  There is also an adaptive component of metabolic rate slowdown that is mediated by changes in hormones: leptin, insulin, thyroid, catecholamines.  As these change (decrease) on a diet, you find that tissues burn fewer calories per unit mass.  I’d mention that not all studies find this, about half do and half don’t.  That is, your assumption that a given body composition always burns the identical number of calories on a day to day basis isn’t entirely correct.

Of course, an important question is how much of a change this amounts to.  During active weight loss, the impact is relatively greater (because hormones tend to be more greatly affected); at weight maintenance (once a person has stabilized), the impact isn’t huge.  In some studies of the post-obese (folks who have been dieted down and maintained at that weight) show a relatively modest 5% or so reduction in RMR.  The effect exists but is not massive; it’s also highly variable, with people showing relatively more or less of an effect.

There is also evidence that individuals move around less when they lose/are losing weight.  As James Krieger recently wrote on his Weightology.net website, it looks like changes in activity (especially NEAT) are the far larger contribution to the reduction in overall energy expenditure on a day to day basis; the number of calories burned in that activity also appear to be reduced due to improved muscular efficiency.

In that study, decreases in RMR were about 150 calories per day but reductions in activity expenditure were up in the 300 calorie plus range with the total effect being over 400 calories.  This is likely why daily activity has such a profound impact on weight maintenance as I discussed in Exercise and Weight/Fat Loss Part 2: since the body is ‘automatically’ decreasing activity energy expenditure, you have to make up for it.

So basically you’re both correct and incorrect.  The greatest impact on total daily energy expenditure certainly appears to be due to decreased spontaneous activity during the day. However, there is also an added component of a reduction in resting energy expenditure due to changes in RMR, even with complete maintenance of lean body mass.  Some of this is due to simply being smaller, some of it is an adaptive reduction in metabolic rate due to shifting hormone levels (which, again, not all studies find).

And semi-tangentially, a long while back I had written an article as a background primer to something I had intended to write about alcohol.  Well, now I don’t have to since Martin Berkhan over at Leangains.com has written it.   In his article The Truth about Alcohol, Fat Loss and Muscle Gain he pretty much covers everything you could ever want to know about the topic.

Answer: The short answer, as you might have guessed is no.  Now, as always, here’s the longer answer.

I suspect that the idea that one needed to eat fat to burn fat came out of a misunderstanding of some of the early literature on low-carbohydrate/high-fat/ketogenic diets (note: I’m defining a ketogenic diet here as any diet that contains less than 100 grams of dietary carbohydrate; a topic discussed in more detail in my first book The Ketogenic Diet).

In those studies, there was clearly an increase in the body’s use of fat for fuel (indicated by a large scale decrease in something called the respiratory exchange ratio or RER) and I have a hunch that people assumed that it was the huge increase in dietary fat that was driving the increase in fat burning.

But as I discussed in Nutrient Intake, Nutrient Storage and Nutrient Oxidation as well as in How We Get Fat, the burning (oxidation) of fat isn’t really related to fat intake per se.  Rather, it’s related to carbohydrate intake.  That is, the act of eating dietary fat doesn’t usually have a major impact on how much fat you burn.   I say ‘not usually’ as some studies find that very high fat intakes (like 80 grams all at once) have a small effect on fat oxidation by the body. But for the most part, how much fat the body burns during the day is related primarily to carbohydrate intake, secondarily to protein intake, and almost not at all to dietary fat intake itself.

Also consider that the following three conditions:

1. Complete fasting (no food intake at all)
2. A high-fat, low-carbohydrate ketogenic diet (e.g. 30% protein, 65% fat, 5% carbohydrate)
3. A protein sparing modified fast (PSMF, such as my own Rapid Fat Loss Handbook)

All generate basically the identical shift in the body’s fuel utilization: a decrease in resting RER indicating a shift to using predominantly fat for fuel.  Again I say basically since both the ketogenic diet and the PSMF will be marginally different than complete fasting due to the intake of dietary protein.  But for the most part, the shift in fuel use by the body is identical in all three conditions, you see a huge drop in RER indicating a massive increase in the use of dietary fat for fuel.

And the commonality in all of those conditions is not the presence or absence of dietary fat (diets 1 and 3 have little or no dietary fat, diet 2 has quite a bit).   Rather, it’s the lack of dietary carbohydrates.   Which, based on what we know about how the body determines fuel usage makes sense.  As I discussed in the linked articles above, when you eat more carbs, you burn more carbs (and less fat); eat fewer carbs and you burn fewer carbs (and more fat). Which means that in all three conditions above it’s the absence of dietary carbohydrates driving the increase in fat burning, not the presence of dietary fat.

Which isn’t to say that increasing dietary fat intake under some conditions can’t have benefits (such as increased fullness, food enjoyment or flexibility, limiting the daily deficit to moderate levels if that’s the goal, etc.) which are discussed in other articles on the site (I’d suggest the Comparing the Diets series for an overview of different dietary approaches).  It’s simply that increasing fat burning per se simply isn’t one of them; rather, that’s accomplished by reducing carbohydrates and total caloric intake.

Hope that answers your question.

Answer: The above question actually came through in the comments section of Exercise and Weight/Fat Loss: Part 2 and I thought it was important enough to address explicitly since it’s a place where I still see many mainstream diets and dieters making mistakes.   It’s worth noting that bodybuilders and other strength athletes have been promoting higher protein intakes while dieting for decades and this is yet another place where modern science has ended up validating those beliefs many years after the fact.

The question of adequate protein under different conditions is one that has a long history of debate, the issue of maintenance requirements as well as protein intakes for athletes is still highly debated with science on both sides of the story (for details you can refer to The Protein Book).

With regards dieting specifically, this was a topic of much study in the 60’s and 70’s as researchers started looking past the simple issue of weight loss and into that of changes in body composition; the goal moved from weight loss per se to that of generating fat loss while minimizing lean body mass and muscle mass loss.

After much toing and froing and research had been done it was eventually found that a protein intake of about 1.5 g/kg of lean body mass (LBM; note that researchers actually used Ideal Body Weight but this is a rough proxy for LBM) was necessary to spare LBM losses in a non-training obese individual consuming low calories.

This is about double the DRI for protein (at 0.8 g/kg) at maintenance calories.  So for an overweight individual at say 200 pounds and 30% body fat (this would give them an LBM of 140 lbs or 63 kg), that would be a protein intake of 95 grams of protein per day.   Please note that this value is simply a minimum and dieters may still find that higher protein intakes are beneficial from a hunger blunting effect or what have you (see below).

In that context, I’d mention that at least one of the studies I referred to in Exercise and Weight/Fat Loss: Part 2 that found no benefit of resistance training gave something like 40 grams of protein to the subjects; far less than necessary or adequate.  So it’s no surprise that no protein sparing effect of exercise was seen; the diet was inadequate in the first place.

It’s worth noting that more recent research supports further benefits of increased protein intakes while dieting, beyond simple lean body mass maintenance.  Protein is the most filling nutrient (meaning that higher protein intakes tend to control hunger better) and studies have found that higher protein intakes can help to stabilize blood sugar levels while dieting which has benefits from both an energy level and appetite standpoint.  Protein high in the amino acid leucine (with the dairy proteins whey and casein being the two proteins highest in leucine) seem to have extra benefit in this regard.

Now, as individuals get leaner, protein requirement tend to go up further for reasons discussed in other articles on this site.  As well, regular training tends to further increase protein requirements.  So lean athletes trying to lose fat while sparing lean body mass loss need even higher protein intakes than this.  And we’ve known for decades now that caloric intake per se tends to impact on protein requirements; as caloric intake goes down, protein requirements go up. And vice versa.

While less data on this group is available, bodybuilders and athletes have long used a protein intake of 2.2 g/kg (1 g/lb) lean body mass as a generalized intake level and as folks get very lean, intakes of 3.3 g/kg (1.5 g/lb) of lean body mass may be required to stave off muscle loss while dieting.  In some very extreme cases, such as the near protein only diet approach of my own Rapid Fat Loss Handbook even higher protein intakes may be required for very lean individuals.

So basically we have an intake continuum ranging from about 1.5 g/kg (0.68 g/lb) as a minimum for the obese non-training individual up to a high of around 3.3 g/kg (1.5 g/lb) of protein per pound of lean body mass for very lean heavily training athletes or bodybuilders with middle ground values being found in between those two extremes.  You’ll note that I didn’t put any of those values in terms of percentages for reasons discussed in Diet Percentages: Part 1 and Diet Percentages: Part 2.

So that’s what I mean by ‘adequate protein on a diet’ when I use that phrase.  It’s context dependent with the primary variables being body fat percentage (as this goes up, protein requirements go down), caloric intake (as caloric intake goes down, protein requirements go up and vice versa), and activity (with regular activity generally increasing protein requirements).

Certainly larger amounts of exercise can approach significance (and as folks become fitter, they can burn more calories with activity) but the idea that a little bit of exercise is going to have a massive impact on anything is fairly misguided.  However, there are more ways that exercise might positively impact on weight/fat loss (especially when combined with changes in diet) and that’s what I want to look at today.   I’d mention that readers should check out PJ Striet’s comments in Exercise and Weight/Fat Loss: Part 1 for some other potential benefits of exercise outside of weight and fat loss per se.

Quality of Weight Lost

In Exercise and Weight/Fat Loss: Part 1 I sort of confusingly jumped back and forth between weight and fat loss (mainly using fat loss as a way of estimating how much exercise might actually impact on things); for the most part the big meta-analyses and a lot of studies have focused more on total weight lost in response to exercise with most of them finding, at best, a small impact.

However, anyone who hasn’t had their head under a rock for the past couple of decades, or who has read anything on this website, knows that there is more to the overall equation than just weight loss.  As I discuss in some detail in What Does Body Composition Mean? the body is made of a number of different components including muscle mass, organs, water, connective tissues, minerals, fat, etc.

Just looking at changes in body weight can be misleading; it’s more important to look at what’s happening to body composition; that is, under most circumstances, folks want to lose fat while minimizing or eliminating the loss of lean body mass (especially muscle mass).

Does exercise help with that? That is, does the addition of exercise to a diet change the proportion of what’s lost; that is does it change the quality of weight lost (ideally shifting the loss towards more fat and less muscle mass).  And when you look at the studies the answer is a big old it depends.  A lot of which has to do with the specifics of the diet (especially the amount of protein provided) and the type of exercise done.

For the most part, exercise is found to have a protein sparing effect of some sort; that is less muscle and more fat is lost in response to the same caloric deficit.  It’s not universal with not all studies finding an impact (depending on the, type, frequency, duration and intensity of activity) but certainly the trend is for that.

And here is a place where there does seem to be a difference in what type of activity being done with studies (and practical experience) finding that resistance training (especially coupled with adequate protein intake) being superior to aerobic activity (or a low protein intake) for limiting lean body mass loss and, thus increasing fat loss in response to a diet.  And while more mixed, there is some suggestion that this helps to limit the normal drop in metabolic rate that tends to occur with weight loss.

Put differently, as I phrased it in The Rapid Fat Loss Handbook, if there’s a single type of exercise to do while dieting, it’s proper resistance training.  Coupled with an adequate protein intake, that alone tends to limit (or eliminate) lean body mass losses such that the weight which is lost (in response to the caloric deficit) comes predominantly from fat mass.

So this is a place where even if exercise doesn’t increase the quantity of total weight loss per se (i.e. how much the scale actually changes), it can impact on the quality of weight lost; with proper exercise causing more fat and less muscle loss than would otherwise occur.  Here again, proper resistance exercise, especially coupled with adequate protein, seems to be superior to aerobic activity or diets with insufficient protein.  You can read more about proper resistance training in Weight Training for Fat Loss Part 1 and Weight Training for Fat Loss Part 2.

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Accountability/Adherence

Perhaps one of the most potentially beneficial places that exercise can play a role during weight loss is with adherence.  I’ve mentioned this in articles before but, for many people, the simple fact of doing some sort of exercise on a given day makes it more likely for them to stick to their diet.  The underlying logic seems to be along the lines of “I worked out today, why would I blow my diet?”

In a lot of ways, this may actually be one of the single most important aspects of successful weight loss attempts, long-term adherence to the plan. I’ve ‘joked’ about this before, saying that the best diet is the one that you can stick to and there is much truth to this joke; at the end of the day after you work through all of the potential benefits of one diet versus another or what have you, the best one for a given individual is the one that they can stick to in the long-term.  If regular daily activity of some sort helps an individual adhere to their dietary plan, that benefit alone may be more important than any actual metabolic effects of the exercise bout itself.

Basically, for some people there seems to be a psychological coupling of exercise with good dietary habits on a day to day basis and clearly that can be of benefit.  Of course, there is a potential negative that needs to be considered: when/if people stop exercising often their dietary habits fall off just as quickly.

In fact, one odd study years ago looked at this issue comparing diet, exercise and diet+exercise for both short- and long-term results.  It found that the diet+exercise group ran into problems such that, when subjects stopped exercising, their diet habits fell apart too.

There is another potential place that this can backfire which I’m going to look at next.

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Exercise and Hunger/Appetite

The impact of exercise on hunger and/or appetite is, to put it mildly, complicated.  This is because human hunger/appetite (I’m not going to bother making the distinction between the two here) is exceedingly complex being an interplay of biology, psychology and environment.  These are often separated out for convenience but they all interact.

Looking solely at biology, overall exercise seems to have a beneficial overall impact on acute hunger, showing a decrease at least in the short-term (other work has shown that the overall hunger/appetite regulation system works more effectively when regular activity is performed).

This seems to be related to increased levels of various gut hormones involved in signalling fullness, as well exercise can increase leptin transport into the brain (other studies suggest that long-term aerobic activity may improve leptin sensitivity which is good given that obesity is generally associated with leptin resistance in the brain).    There may still be as of yet undiscovered mechanisms for exercise to impact on hunger/appetite.

Other work suggests that even if exercise can increase hunger, any increase in food intake tends to be less than the energy burnt during the activity itself; that is exercise still has an overall benefit.   It’s worth mentioning that even here there tends to be a large degree of individuality, some people compensate for the energy expenditure of activity better than others and this may be part of what contributes to individual differences in results.

One thing I noticed years ago (and forgot to mention in the Training the Obese Beginner series) is that beginners often seem to get a slight increase in hunger following activity, at least in the first few weeks of training.  I suspect this is due to their general over-reliance on glucose for fuel (falling blood glucose being one of many stimuli for hunger).   At about the week 4 mark, as their bodies started to get the first adaptation to training and started to use more fat for fuel; this effect generally went away.

It’s worth noting that emerging research suggests that there may be gender differences in this effect (along with many others) with women, as usual, getting the short end of the stick when it comes to exercise and hunger regulation.  And this is consistent with earlier studies showing that, under uncontrolled eating conditions, women are less likely to lose weight in response to exercise than men.

Of course, the above tends to interact massively with the psychology of the individual and whether or not they are consciously controlling their food intake.  That second issue is a major confound in a lot of studies that people tend to forget about when they compared different studies.

However, this isn’t always the case and one trap that many exercisers often fall into is assuming that their exercise bout has burned far more calories than it has (you’ll hear folks figuring they must have burned at least 1000 calories in an hour of moderate activity when the reality is probably closer to 400-500) and figuring that they’ve ‘earned’ that big post-exercise junk-food meal.

As I mentioned in Exercise and Weight/Fat Loss: Part 1 it’s usually quite trivial to overcome all but the most massive exercise related energy expenditures.  You can put down 1000+ calories in a big post-workout meal with ease, more than compensating for the energy burn of the activity.

But as much as anything I feel that this comes down to an issue of misinformation and education; people need to be realistic about the number of calories they are burning during activity.  It’s simply almost never as high as they think and realizing this is a first step to avoiding habits that will tend to not only offset but actually reverse any beneficial impact of activity.

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Weight Loss Maintenance

As a final topic, I want to look at an issue that is perhaps more important in the big scheme of things than actual weight loss per se.  The rather simple fact that needs to be recognized is that weight/fat loss per se isn’t really the hard part; people consistently do and can lose fat/weight all the time.

The issue is with keeping it off.  That is to say, although people successfully lose weight/fat all the time, they usually end up gaining it back. Frankly, I am of the opinion that strategies to lose fat/weight are no longer the important issue, rather research and practice needs to find out what makes people so poor at long-term adherence to dietary changes (or behavioral changes of all types) and find solutions to that.  Is it biological, psychological, is the distinction even meaningful?  And how do we fix it?

But beyond that issue, this is one place where exercise has routinely shown to have a benefit with regards to overall body weight/body fat reduction programs.  That is, while most studies have not found a massive impact of exercise on weight/fat loss per se, the impact on weight loss maintenance seems to be much much larger.

Both epidemiological and intervention studies have found that maintenance of regular activity following weight loss is associated with better long-term weight maintenance (I’d note that keeping protein intake high also has benefits) but with one major caveat: it takes quite a bit of activity (I’d note that this seems to assume that the diet is relatively uncontrolled after the active weight loss period).

Various lines of research suggest that a weekly exercise energy expenditure of 2500-2800 calories per week is required to maintain the lowered body weight.  If we assume an average of 5-10 cal/min for low to moderate intensity activity, this works out to between 280-500 minutes of exercise per week or somewhere between 40-70 minutes of activity (depending on intensity and frequency) per day.

Again, the above seems to assume that the diet is relatively more uncontrolled following the actual weight-loss intervention which isn’t automatically a good assumption.  But it does put into perspective what may be required in terms of daily activity to maintain weight loss.

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Summing Up

So that’s a (for me anyhow) fairly brief look at the potential impact of exercise on weight/fat loss.  As I discussed in some detail in Exercise and Weight/Fat Loss: Part 1, the unfortunate reality is that all but the most extensive exercise programs are unlikely to have much of an overall impact on the absolute quantity of weight lost, especially in the absence of dietary changes.

The average beginner/overweight individual simply can’t burn enough calories in realistic amounts of exercise to have much of an impact.  Reducing caloric intake through various means (discussed in detail in other articles on the site) will almost always have a larger impact on overall energy balance.

However, that doesn’t make exercise useless and there are other ways that activity can positively (and negatively) impact on the overall goal of weight/fat loss.  The first of those is in shifting the quality of weight lost; even if exercise doesn’t affect the total magnitude of scale change, proper activity (with resistance training coupled with sufficient protein intake being superior to aerobic work/low protein) can decrease the loss of lean body mass and increase the total loss of fat.

There are also potential benefits to adherence/accountability with some people essentially coupling daily activity with adhering to their diet.  Anything that makes someone stick to their diet in the long-term can only be beneficial. As noted, this can sometimes backfire, where the person then loses all good dietary habits if their exercise program is interrupted for whatever reason.

In terms of hunger and appetite, exercise seems to have an overall beneficial impact but interactions with the individual psychology of the dieter can affect this greatly; some people will rationalize the consumption of food based on a misunderstanding of their actual calorie burn.  This can completely overcome any benefit of the exercise in terms of energy expenditure.

Finally, exercise appears to have the greatest potential benefit in terms of long-term weight loss maintenance; here studies have shown that regular exercise improves long-term weight loss maintenance.  However, it takes quite a bit with upwards of an hour or more of daily activity required to completely offset post-diet weight gains.

I suppose the issue isn’t really one of the realities of exercise and fat/weight loss but rather how the message was misinterpreted.  Many have held up exercise as some sort of panacea for all things, health, fitness and of course what everyone is really interested in: losing weight/fat and I suspect the message got a bit garbled as it so often does: people figured that they could do a bit of easy exercise and the pounds would just melt right off.

The realities, unfortunately, are often quite a bit different and in this series of articles (which I’ll hopefully keep to a mere two parts), I want to look at the possible ways that exercise might impact on one’s overall body recomposition goals.  You’ll notice that I used the word ways plural in that sentence; while most focus on the direct role of exercise on fat loss (via direct calorie and/or fat burning) it turns out that there are more ways than just that for exercise to impact on things.

For the most part, I’m going to sort of cluster all exercise in one big grouping for the sake of simplicity.  Clearly resistance training and aerobic training aren’t the same and have differential effects; when needed I’ll make distinctions between them.  It’s important to realize that most research on exercise and fat loss have used obese individuals (researchers by and large not being interested in lean folks trying to get leaner) and that has potentially other impacts on a lot of this.  Again, as needed, I’ll make note of this.

Today, since it will take the most verbiage, I’m only going to look at the primary way that exercise can (or can not) impact on body recomposition goals and that is in terms of its impact on total weight loss; that is the quantity of weight lost.  I’ll note ahead of time that I am going to confusingly jump back and forth between fat and weight although they are not the same thing.  This will make more sense in Part 2 when I attempt to cover all of the other ways that exercise may potentially impact on things.

Quantity of Weight Loss

Most commonly, exercise is held up as a way of either directly causing weight/fat loss or for increasing the amount of weight/fat lost when added to a diet with the focus primarily on the direct effects of exercise on calorie/fat burning either during the exercise bout or afterwards.   As noted above since it will take the longest, that’s the only issue I’m going to look at today.  Basically, I’m going to give a reality check on the impact of realistic amounts of exercise in terms of its impact on body weight/body fat.  It’s not a reality many are happy with.

In previous articles as well as in my books, most recently in the Training the Obese Beginner series, I’ve made the comment that, generally speaking, the only people who can burn a tremendous number of calories during exercise are trained athletes; and they aren’t the ones that usually need it.  That statement appears to have confused some people but the point I was trying to make is that the number of calories that can be burned with realistic amounts of exercise in beginners is usually fairly low.

In my first book The Ketogenic Diet, I cited some paper or another indicating that most untrained folks can burn perhaps 5-10 cal/minute in exercise if you’re talking about sustainable intensities; this might hit 15 cal/minute but that would be for high intensity interval-type training.

However, the duration of that activity tends to be exceedingly limited and the total average calorie burn for the activity will be lower due to the rest intervals.  As well, this isn’t an intensity of training that can be done frequently.   Even achieving 10 cal/minute would be fairly challenging for an relatively untrained/low-trained individual.

Of course, as training status goes up, folks can burn proportionally more calories.  A moderately trained individual might be able to burn 10 cal/minute fairly easily and hit 15 cal/minute for extended periods if they are willing to work a bit.  20 cal/minute might be achievable for short periods but, again, the total burned during activity would be balanced out by the low intensity nature of the rest intervals.

As I discussed in Steady State vs. Intervals and EPOC: Practical Application, when I have compared interval sessions of varying types to steady state training with a Powermeter, the total caloric expenditure is usually about identical because of how the rest intervals affect the average intensity.  The steady state sessions are far easier to complete and can be done more frequently as well.

A very highly trained athlete might be able to burn 15 cal/minute as a matter of course, 20 cal/minute if they are willing to work and hit even higher values for high intensity training.  Certainly these athletes sometimes need to drop fat (usually to improve power to weight ratio) and they have the advantage of being able to burn a tremendous number of calories with even low intensity activity.   Simply tacking on an ‘easy’ 30-45 minutes to their normal training can burn a pretty large number of calories making fat loss relatively easy without much change in diet.  But that last group is not who we are realistically talking about here.

I’d note that the above values are for cardiovascular activities.  People always ask about calorie burn during weight training and it’s harder to pin down values.  It also depends staggeringly on the type of activities done (e.g. whole body vs. isolation exercises), rest intervals, rep ranges, etc.    Clearly repetition clean and jerk will burn a lot more calories than barbell curls.

On average, studies have found a calorie burn of 7-9 cal/minute seems to be about right (again with huge variability) but that only holds for the actual work time and a lot of time in the weight room is usually spent resting.  When we have tracked calorie burn for various types of weight training (ranging from Olympic lifting to isolation machine work) with tools such as the Bodybugg/GoWearFit or Polar heart rate monitors, a calorie burn of 300-400 cal/hour is about the average.

So with the above values in hand, let’s look at realistically what we might expect in terms of weight loss using the values for a typical untrained/low fitness level individual assuming a calorie burn of 5-10 cal/minute and various durations and frequencies.   I’m going to compare 30 vs. 60 minutes and 3 vs. 6 days/week to estimate total caloric expenditure.

And here’s where the confusing bit comes in, to put in this in real world terms I’m going to move from weight loss to fat loss with the assumed value of a 3500 calorie deficit to lose one pound of fat; of course this assumes that 100% fat is being lost which is not always a safe assumption.  I’d note that total weight lost will be higher if a larger proportion of muscle is lost, an issue I discussed in The Energy Balance Equation.

I want to note up front that there is a HUGE assumption built into the following calculations: that nothing else is changing.  Not diet, not activity at other times during the day (some studies find that people compensate for exercise based energy expenditure by moving less later in the day), nothing.  The only change we’re making here is by adding exercise to an otherwise static situation.  For reasons far beyond the scope of what I want to talk about right now, this is not a good assumption.  It simply makes the math easier.

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Frankly, the results are pretty dismal; you don’t even get to a one pound fat loss per week until you reach 6 days/week of an hour of fairly challenging exercise every day.  Certainly the folks who think that brisk walking for 30 minutes a few times per week is going to have a major impact on much of anything without a complete overhaul in diet are incorrect; the impact is simply negligible.

It’s also worth mentioning that the above caloric expenditure is actually somewhat of an overestimation since it includes the calories that would be burned by simply sitting around doing nothing.  That is, if you did nothing during that hour, you’d burn perhaps 60-100 calories/hour or so depending on that activity.  The above values include that resting expenditure so the actual impact on energy expenditure above and beyond normal are going to be slightly lower.

But it’s fairly easy based on the above values (which again represent a massive number of assumptions in the first place) to see how many people have concluded that exercise is worthless for fat loss.  And certainly a majority of studies (including most of the big meta-analyses) have reached that conclusion: compared to dieting alone, exercise tends to add very little to the quantity of weight lost.  Even added to a diet, exercise tends to impact on the total weight loss marginally at most; the diet is doing most of the work in terms of the actual quantity of weight lost (here I’m switching back to talking just about weight).

And this is simple mathematics, removing 1000 calories/day from the diet can be achieved with relatively more or less ease (depending on how bad the diet is to start with); the average beginner simply can’t burn that many calories with any realistic amount of exercise.  At a low intensity and a calorie burn of 5 cal/min, that would require 200 minutes of activity per day, over 3 hours.  At a challenging 10 cal/min, you’re looking at 100 minutes, an hour and forty minutes.  This is simply beyond what most people can, are willing, or have time to do.

This is also why I mentioned the huge assumption that diet is unchanging in the above estimations; another conclusion often reached is that exercise is worthless as the amount of calories that can be burned can be offset by even a small increase in food intake.  An average bagel may contain 250 calories (or more if they are the big ones), you can overcome the deficit generated by the lower amounts of activity with a small increase in food intake.

I’d mention that the only impact of exercise on weight/fat loss tends to be due to the deficit created; studies where the calories from activity are replaced by increasing food intake show no changes in anything.  That is to say, if you compensate for the activity by eating more (an issue I’ll talk about later), nothing really happens.

In this vein, most of the exercise and diet studies have used fairly low-moderate amounts of activity (in line with the above chart) and few have progressed anything over the course of the study, volume or intensity; most show neglible effects on much of anything (even the much vaunted interval studies only show maybe a 1-2 lbs fat loss over 12 weeks compared to steady state training).

The latter is a problem to me since no good fitness program would be so static without some progression in frequency, duration, intensity or all three as folks got fitter and were able to handle more or harder training.  As I mentioned in the Training the Obese Beginner series, one consequence of regular fitness training is an improvement in fitness, allowing folks to train at higher levels (both driving fitness higher as well as burning more calories).

So while realistic amounts of exercise may not be able to play a major role initially in weight loss, over time it not only adds up (albeit in depressingly small amounts) but can end up contributing further down the road as fitness improves.   That’s in addition to some other indirect ways that exercise may help that I’ll talk about shortly.  Finally, there turns out to be a huge area where exercise has been shown to play a role that I’ll talk about when I wrap up the series.

I’d note before moving on that some studies using fairly large amounts of activity (one that comes to mind had subjects cycle 2 hours/day 6 days/week) have shown a greater impact on weight and fat losses.  But these amounts of activities are usually considered to be fairly unrealistic for most people.  I’m simply making the point that for people who can do a lot of activity (one person on my forum actually got into the habit of doing 8 hours of low intensity cycling during the day believe it or not) there can be an impact.

But the simple fact is that, for the average untrained individual, realistic amounts of activity are unlikely to have massive direct impacts on either body weight or body fat; the caloric expenditure simply isn’t significant enough to impact on anything.  As well, changes in diet have the potential to make a much greater contribution to the creation of a caloric deficit; removing 500 or even 1000 calories per day from the diet can usually be achieved much more readily than adding the same amount of activity.  At least in certain populations.

But as noted in the introduction, there are several other ways that exercise can positively impact on weight/fat loss goals. Those will be the topic of Part 2 on Friday.

Read Exercise and Weight/Fat Loss: Part 2

Background

There has long been a question of why some people seem to be able to ‘eat anything they want’ and remain thin while others can do no such thing; in fact this is often used as an argument that The Energy Balance Equation is wrong.

More in fact, the paper I’m going to talk about today was once trotted out by several individuals as ‘proof’ that The Energy Balance Equation was incorrect.  Unfortunately all their discussion really ended up proving was that, as I suggest in The Energy Balance Equation, the issue was not the equation, but that they had no clue what they were talking about.  But I’m getting ahead of myself.

Certainly we all have seen, known (or in lucky situations been) that person who seems to ‘eat anything they want’ without gaining appreciable weight.  This is in contrast to those people who seem to be able to simply look at food and get fat. What’s going on?

At least part of what’s going on, and this is outside of the paper I’m going to discuss today, is that these folks in question often don’t eat as much as you think they are.  Certainly you may see them gorging on food acutely (at a single meal, perhaps out with friends) but what you often don’t see is what they are doing the rest of the day, or the day before, or the day after.

So while you may see the single enormous meal, what you don’t see is the smaller or non-existent meals that they are eating at other times of the day.  Or the compensations that occur a day or two later to drastically reduce their food intake and keep them in energy balance in the long-term.  So while you may assume that they eat like that all day every day, you don’t know that for sure.

But as it turns out, that’s not all that’s going on.  As I discussed in The Energy Balance Equation one mistake people often make is assuming that the output side of the equation is static; that the energy output of a given individual is invariant over time.  Thus if you plug in X calories and the person doesn’t gain exactly Y weight, the equation must be invalid.  This is wrong for a bunch of reasons discussed in that article not the least of which being that the out side of the equation changes in response to cahnges in food intake, activity and obesity.

For example, in response to both increases and decreases in food intake (as well as body weight), we know that basal or resting metabolic rate (BMR/RMR) can go up and down.  Similarly, the thermic effect of food (TEF) is related to the amount (and type) of food being eaten and will adjust upwards or downwards as well.

Activity of varying sort can be affected by energy intake as well as body weight (e.g. larger bodies burn more calories in movement).  Clearly the idea that the out side of The Energy Balance Equation is unchanging is wrong.  Yet people keep pretending that it is when they simply look at calories in or out and what they think should happen to body weight without accounting for those changes.

But as it turns out, changes in the above three factors don’t seem sufficient to explain some of what is seen when people are overfed with studies finding a huge individual variance in how much fat is gained with identical amounts of overfeeding and that brings me in a very roundabout way to today’s paper; while over 10 years old, this was a seminal study that goes a long way towards explaining the odd observation that some people are seemingly able to ‘eat’ whatever they want and not get fat.   The researchers wanted to try to determine mechanistically what might be causing that to occur.

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The Paper

It’s been known for quite some time that people show a rather large amount of variability in terms of actual fat/weight gain in response to overfeeding and the researchers wanted to try to figure out some of the mechanistic reasons why this might be the case.

Towards this goal, the study recruited 16 people (12 males and 4 female) who underwent body composition measurement (via DEXA) and total energy expenditure (measured by doubly labeled water) who were then overfed by 1000 calories per day for 8 straight weeks.

I’d note that both basal metabolic rate and TEF were measured via indirect calorimetry, mainly to see if changes there could explain anything about the measured results.  As a control, subjects were required to maintain their exercise type activity at very low levels; this was done to prevent folks from trying to compensate for the increased caloric intake by simply exercising more.  While slightly artificial in terms of how people often work in the real world, this was simply a way of controlling the study to see what else might be going on.

Over the course of the study, an average of 432 cal/day was stored and 531 was dissipated through increased energy expenditure: this accounted for 97% of the total (note: this means that the energy equation was essentially balanced in that all calories were accounted for, either being stored or burned; none magically went anywhere else).  However, looking at the averages obscure what was really happening.

Moving to individual results, fat gain varied from a low of 0.36 kg (0.79 lbs) to 4.23 kg (9.3 lbs) a 10 fold variance despite the same 1000 calorie/day increase in energy intake.  Changes in BMR and TEF were unable to explain this difference.  BMR went up only 5% accounting for 8% of the extra energy while TEF went up 14%, simply in response to the increased food intake; none of those changes showed any correlation with changes in fat mass.   As I noted above, exercise type activity was clamped at low levels so changes there can’t explain the difference either.

And that brings us to NEAT, an acronym referring to Non-Exercise Activity Thermogenesis.  As the researchers define it:

NEAT is the thermogenesis that accompanies physical activities other than volitional exercise, such as the activities of daily living, fidgeting, spontaneous muscle contraction, and maintaining posture when not recumbent.

Basically, think of NEAT as the calorie burn associated with all activities that aren’t formal exercise.  And that’s where the researchers saw the massive difference between subjects; while the average increase in NEAT across all subjects was 336 cal/day, the individual changes in NEAT varied from -98 (that is it actually went down in at least one person) to +692 cal/day.

That is, in at least one subject, approximately 700 calories of the 1000 extra was burned off via NEAT.  That’s in addition to the increase in BMR and TEF which would have burned off even more of the total calories.  The researchers calculated that the increase in NEAT in the greatest responder would be the equivalent of strolling for 15 minutes per hour during waking hours.

In this vein, in the review of the Bodybugg/GoWearFit I mentioned that even small increases in activity over the course of the day can end up having a massive impact on overall energy balance because of how it can really add up.  The subjects with the increase in NEAT effectively had that happen without trying.

Of more importance, changes in NEAT directly predicted fat gain (or the lack thereof): people who showed the greatest increase in NEAT showed the smallest fat gain and vice versa.   I’d note in finishing out the paper that the four worst responders in terms of NEAT were the 4 female subjects; this really isn’t news inasmuch as we’ve also known for decades that women get the short end of the stick in terms of both weight gain and loss.

I’d also mention that this paper did nothing to determine the mechanisms behind NEAT (later studies have tried, and done poorly, at determining what is the actual cause of the increase in NEAT) only mentioning that NEAT seems to be a familial trait (suggesting a genetic basis).  Other later studies have shown that NEAT is essentially subconscious, people either do it or don’t.

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My comments:

There’s really not a huge amount to say about this paper; it’s a point of interest without a lot of practical application.  I only bring it up to make the point that many people’s assumptions about what does or does not disprove The Energy Balance Equation tend to stem with their misunderstanding of things; especially their failure to realize that the out side of the equation is not static.  And this goes especially for the NEAT component of energy expenditure, with individual increases in NEAT varying massively from one person to another.

Of more relevance, not only is the out side of the equation not static, there appears to be quite a bit of variability involved.  While some people get effectively no (or a negative) increase in NEAT with overfeeding, which makes their gaining of fat quite easy, others have essentially won the genetic lottery: in response to overfeeding, they subconsciously ramp up small calorie burning activities that add up over the course of the day to burn off the excess.

To beat that dead horse, the equation isn’t wrong, the out side of the equation in terms of NEAT simply differs massively between people especially in terms of the NEAT response.  The people who can apparently ‘eat like gluttons’ and not gain weight appear to have a physiological mechanism by which they burn off the excess, essentially protecting them from fat gain.

In that vein, I’d mention at least one other study that compared the response to overfeeding and dieting in terms of metabolic rate adjustment.  It found that those individuals who showed the greatest increase in metabolic rate to overfeeding showed the least drop in response to dieting; by contrast those people who showed the least increase to overfeeding showed the biggest drop with dieting.

That study posited the existence of spendthrift (big increase with overfeeding/small decrease with dieting) and thrifty (small increase with overfeeding/big decrease with dieting) physiologies.  Clearly the first has as huge benefit in terms of both avoiding weight gain as well as losing it if necessary; the second group will have a much larger problem.

As I mentioned above, follow up work to this seminal paper has done little to determine the mechanisms behind it (which might lead to some way of increasing NEAT in those not disposed to it).  It appear to be genetic and more or less subconscious.  Of course, that doesn’t stop people from consciously trying to do things to increase their activity levels and energy expenditure outside of formal exercise.  All of the old behavioral strategies such as taking the stairs instead of the elevator, parking further away, etc. all end up adding up over time.