Early research into post-workout nutrition focused almost exclusively on endurance athletes and, really, the only issue of importance was refilling muscle glycogen and re-hydrating the athlete.  For this reason the focus was on carbohydrates and fluids with little else considered.  At some point, I recall it being the mid-90′s some early work suggested that adding protein to post-workout carbohydrates was beneficial in terms of glycogen re-synthesis and a new dietary trend started to form.

Now, it turns out to be a bit more complicated than that whether additional protein actually increases glycogen synthesis depends on a host of factors, primarily how much carbohydrate is provided.  Simply, if sufficient carbohydrate is given following training, adding protein has no further benefit in terms of promoting glycogen re-synthesis.

In situations where insufficient carbs are consumed (by choice or otherwise), extra protein helps.  Which isn’t to say that additional protein following training isn’t valuable for endurance athletes even if carbohydrate are sufficient but that’s not really the topic of today’s article.

While individuals involved in the strength sports and bodybuilding were quick to jump onto the post-workout carb/protein bandwagon, the research wasn’t really aimed at them.  As well, there has always been a bit of a disconnect in using work on endurance athletes (who may be doing hours of exhaustive work) and trying to apply it to individuals in the weight room.

Differences in volume of training, fuel use and goals make using data on one group inappropriate for application to the others.  It’s still common to see well-meaning nutritionists use the same guidelines for both strength/power athletes (including bodybuilders) and endurance athletes but that is simply silly.

In any case, work examining the impact of various combinations of post-workout nutrients in terms of promoting strength or hypertrophy would come later and, at this point, a huge amount of work has been done.  I’m not going to get into every detail (the issue is discussed in absurd detail, 35 pages worth, in The Protein Book) of post-workout nutrition and will focus the article simply on the issue of protein, carbohydrates and the combination of the two in terms of how they impact on post-workout recovery and muscle growth.

To understand what I’m going to say and why I think some current recommendations (especially the one saying that you only need protein post-workout) are not consistent with the research, I need to get into a few details regarding how training impacts on muscle growth and how nutrients impact on this.  Don’t worry about the dense text, there’s a pretty graphic below to help explain it all.  A pretty, pretty graphic.

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How Does Muscle Grow?

Endlessly on the site, I’ve talked about how the primary stimulus for growth is progressive tension overload (with fatigue being a secondary factor) but, believe it or not, that’s not what I’m going to talk about here.  Rather, I want to get a bit deeper into the processes of muscle growth.  I’m not going to get full-blown molecular on you, just a bit more detail than I usually go into.

Now, the ultimate goal of getting bigger muscles is, well, getting bigger muscles.  But what does that actually mean?  Skeletal muscle is composed of a variety of different elements including protein (about 100-120 grams of actual protein per pound of muscle and yes I’m mixing grams and pounds), water (making up the majority), connective tissues, glycogen, minerals and a few other things.  I’m going to focus on the actual protein component of it since that’s the bit that actually generates force, etc.

Protein in your muscle is no different than the protein found in dietary protein, it’s a long-chain of amino acids that have been attached to one another in the structure that makes up skeletal muscle (the various fibers and such).  But how does this process work?

Simply, there are two competing processes that go into what ultimately happens to muscle mass which are protein synthesis and protein breakdown.  Protein synthesis is simply the act of attaching amino acids into one another and making them into muscle.  This is an energetically costly process and occurs through the actions of ribosomes (little cellular messengers that you learned about in 7th grade biology) acting under the instructions of mRNA (something else you forgot about from high school).  So training turns on genes which get translated into mRNA which tell the ribosomes what to build and how to do it.  That’s protein synthesis and you can think of it as ‘good’ when it comes to muscle growth.

The competing process is protein breakdown which is the opposite.  Various specialty enzymes work against you, cleaving off amino acids from the already built skeletal muscle. This happens under the influence of hormones and other factors.  Most tend to think of protein breakdown as ‘bad’ in the sense of muscle growth but it’s a touch more complicated than that.  The ability to break down and rebuild tissues in the body (a process which is ongoing constantly, even when you’re ‘at rest’), provides the human body with a lot of adaptations flexibility.  That is, it allows the body to adapt to changing demands and remodel itself based on the signal it gets from whatever is going on in your life.  In that sense, protein breakdown is not ‘bad’.

Now, what happens to your muscle mass ultimately depends on the balance between these two competing processes.  I’ve tried to illustrate this below with three possible scenarios.

1. Protein synthesis > Protein breakdown = Muscle mass increases
2. Protein synthesis = Protein breakdown = No change in muscle mass
3. Protein synthesis < Protein breakdown = Muscle mass decreases

Assuming your goal is bigger muscles, clearly 1 is the goal.  But this also means that there are two primary ways that we can potentially impact on muscle growth.  We can either increase protein synthesis, decrease protein breakdown or do both at the same time.  And doing both at the same time would be expected to have the biggest impact.

There’s one more factoid you need to know which is this: heavy resistance training increases the rates of both protein synthesis AND breakdown.  That is, training doesn’t just turn on one or another, it turns on both.  This is probably a mechanism to help with the previously mentioned remodeling process.  But both happen following training.

And with that background, now let’s look at how nutrients interact with all of this.

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Protein, Carbohydrates or Both, Oh My!

While athletes are rarely that interested in technical details and only want the practical applications, to understand everything I want to talk about I need to look at a bit more detail, specifically how protein and carbohydrates interact with the processes of protein synthesis and breakdown discussed above.  And it basically works out like this:

1. Protein (amino acids) stimulate protein synthesis but have no impact on protein breakdown.
2. Insulin (secondary to carb consumption) inhibits protein breakdown with no impact on protein synthesis.

It’s actually a touch more complex than this.  Protein can impact on protein breakdown under certain conditions and insulin can impact directly on protein synthesis (and there happens to be a big difference in terms of what happens at rest vs. after training).  But for the most part, following training, the above will hold true.

Which leads us towards an ideal of post-workout nutrition. First and foremost I should point out that if you train and don’t eat anything afterwards (and this assumes you haven’t eaten a few hours before), the body will actually remain in a net catabolic state.  That is, protein breakdown will be greater than protein synthesis.  That’s bad.  But only really applies if you’re training first thing in the morning after a fast (how many studies are done) and haven’t eaten anything.

But let’s assume that you eat something following training.  Should it be protein, carbs, both, or some other combination?  First let’s look at the single feeding studies.   That is, let’s say that you could only choose one or the other following training, which should you choose.  The answer there is clearly protein alone which will be vastly superior to carbohydrate alone.  Because while consuming carbohydrates will decrease protein breakdown, only protein will increase protein synthesis (and provide the building blocks for building new muscle).

And this is also where a rather silly idea has come from in the post-workout recommendations.  Folks will often state that “You only need protein post-workout because carbs don’t effect protein synthesis.”  This is true but ignores the impact of decreasing protein breakdown on net protein gain.

Certainly increasing protein synthesis appears to be relatively more important than decreasing protein breakdown but the simple fact is that you get the biggest overall effect if you target both at the same time.  Which means a combination of protein and carbohydrates.

I should probably mention dietary fat and the simple fact is that fat intake post-workout is woefully understudied.  One study found no difference in anything with a meal containing fat vs one not-containing fat (so you folks insanely obsessed with not slowing gastric emptying by consuming dietary fat can stop worrying) but beyond that there’s little research.  One study did find that full fat milk promoted protein synthesis better than skim milk following training but nobody is sure why.  It wasn’t because more calories were consumed because the researchers also tested enough skim milk to match the calories of the whole milk; whole milk was still superior.

In any case, that’s the overall conclusion that I draw from looking at the body of literature: while protein alone is superior to carbohydrates alone, the combination of the two will have the greatest impact on promoting muscle growth (as well as having other beneficial effects on muscle glycogen, etc).  How much of each?  Well that depends on a host of other factors that will have to wait for a later article (or see The Protein Book).

I’ve shown this schematically in the graphic below, showing how both training and nutrients impact on the processes discussed above.

Arrows are neat!

So that’s that: protein is better than carbohydrate following training but protein plus carbohydrates is optimal. Good luck with your muscles.

Dieting

So you start your diet, reducing carbs, calories or both. Blood glucose and insulin levels are going to be reduced. This is good, it releases the ‘block’ on fat mobilization. Additionally, catecholamine release typically goes up, further increasing fat utilization. Blood levels of fatty acids will start to increase. This is good, as it tends to promote fat burning in tissues such as liver and muscle. This effect is facilitated if you deplete liver and muscle glycogen as glycogen depletion tends to increase the use of fatty acids for fuel. The increas in blood fatty acid levels also has the short-term effect of causing insulin resistance which, as I mentioned, is a good thing on a diet since it spares glucose and helps promote fat oxidation. So far, so good, right?

Unfortunately, those are the good effects. Along with this, a lot of bad things start to happen. Although the drop in insulin causes better fat mobilization, it causes other problems. One is that testosterone will bind to sex-hormone binding globulin (SHBG) better, lowering free testosterone levels. As well, insulin is anti-catabolic to muscle, inhibiting muscle breakdown. The increase in cortisol that occurs with dieting enhances protein breakdown as well as stimulating the conversion of protein to glucose in the liver. Cortisol also prevents the amino acid leucine from stimulating protein synthesis. Additionally, a fall in energy state of the muscle impairs protein synthesis (although it increases fatty acid oxidation). The mechanism behind this is more detail than I want to get into here.

On top of that, high blood fatty acid levels tend to impair the uptake of T4 (inactive thyroid) into the liver. There are also changes in liver metabolism that impair the conversion of T4 to T3 (active thyroid). There is some evidence that high blood fatty acid levels causes tissues to become resistant to thyroid hormone itself (this is part of why just taking extra thyroid on a diet doesn’t fix all of the problems). There is also a drop in nervous system output (that can occur in as little as 3-4 days after you start a diet). Along with the drop in thyroid, insulin and leptin, this explains a majority of the metabolic slowdown that occurs. The change in liver metabolism (and the reduction in insulin) also impairs the production of IGF-1 from GH.

With caloric restriction comes a drop in leptin which causes various effects on tissues such as muscle, liver and fat cells. Additonally, a hormone called ghrelin (released from the stomach and responsive to food intake) will go up. The interaction of these three hormones (and probably others) send a signal to your brain (lateral hypothalamus) that you’re not eating enough (do note that the response is not immediate, there is a lag time between the changes in all of these hormones and the body’s response).

This causes changes in the various neurochemicals such as NPY, POMC and the rest to occur, signalling further changes downstream. Levels of testosterone fall (along with the increased binding to SHBG) along with an increase in cortisol, these both tend to have a negative effect on muscle mass. In addition to the problems with conversion mentioned above, thyroid output tends to decrease over time; I already mentioned the drop in nervous system output.

All of these adaptations serve two main purposes. The first is to slow the rate of fat loss, as this will ensure your survival as long as possible. Related to that, the body tends to shut down calorically costly activities. This includes protein synthesis, reproduction and immune function; there’s little point keeping any of these functioning when you’re starving to death. The drop in leptin, and the changes in hormones that occur are a huge part of why men tend to lose their sex drive (and ability) and women lose their period when they get lean/diet hard.

The second is to prime your body to put fat back on at an accelerate rate when calories become available again. As I mentioned earlier, this makes perfect evolutionary sense, even if it presents a huge pain in the ass to us. Ok, enough about dieting, what about overfeeding.

Overfeeding

To a great degree, most of the adaptations that occur with dieting reverse when overfeeding. Actually, that depends a lot on the situation. As I mentioned above, the body as a whole tends to defend against underfeeding better than it does against overfeeding; which is why it’s generally easier to gain weight than to lose it. Studies where leptin has been increased above normal (i.e. to try and cause weight in overweight individuals) have generally borne this out: except at massive doses, raising leptin above normal does very little.

There are a few reasons for this. One theory is that normal leptin levels send essentially a 100% signal, that is they tell the body that all systems are normal. It should seem clear that raising leptin above 100% isn’t going to do much. Another problem is something I alluded to above: leptin resistance. It’s thought that people have varying degrees of leptin resistance which means, in essence, that they don’t response as well to leptin as they should. On top of this, when leptin levels go up, it appears to stimulate resistance to itself. That is, when leptin gets and stays high, it causes you to become resistant to its effects.

Both theories make good evolutionary sense. Your body doesn’t want to be lean but it doesn’t really mind getting fat. If calories are available all the time, it would make little sense for you to get full and/or start burning them off. This is what would happen if you were extremely sensitive to leptin. So high levels of leptin induce resistance to itself; keeping you hungry and eating while the food is available.

But we’re not really talking about raising leptin above normal here, we’re talking about reversing or preventing the drop that occurs with dieting. In that situation, many of the above adaptations will reverse to one degree or another (depending on how lean you are, how long you diet, and how long you overeat).

So now you increase your calories and carbs. This raises blood glucose and insulin, reversing the binding of testosterone to SHBG; cortisol also goes down. With increased carbohydrates, you increase both liver and muscle glycogen. In the muscle, while this decreases fat oxidation, this improves protein synthesis (along with the increase in insulin and testosterone and the decrease in cortisol).

Of course, with increasing insulin, there is a decrease in blood fatty acid concentrations which improves insulin sensitivity. Skeletal muscle insulin sensitivity is enhanced even more by exercise.

The decrease in blood fatty acids, along with changes in liver metabolism will improve both the uptake and conversion of T4 to T3; along with improvements in nervous system output, this will help to increase metabolism.

And, of course, there are all of the central adaptations that occured during dieting, that will reverse to some degree while overfeeding. Leptin will go up (noting that it goes up more quickly than bodyfat comes on) along with insulin, ghrelin goes down. This signals the hypothalamus that you’re eating again, and many of those changes will reverse. So NPY, CRH, POMC and the rest go back towards normal, helping to renormalize all of the hormones that were screwed up in the first place.

To a very limited degree, some of these adaptations would be expected to try and limit fat gain and, to a very limited degree, this is what happens. But, as above, the body is better at preventing weight loss than weight gain.

Summing Up for Now

Ok, let’s put the above two sections together in chart form so that it’s easier to see. A + means an increase while a – means a decrease.

So now, in greater detail, you’re starting to understand the problems involved, especially for the genetically normal. Underfeeding is necessary for fat loss but will always have a negative impact on muscle mass. It also induces any number of adaptations that tend to prevent further fat loss. Overfeeding is necessary to gain but will always have a negative impact on fat mass. However, it can reverse many (if not all) of the adaptations that occur with dieting.

A Final Note on Leptin

Hopefully the above sections have made you realize that there is far more to the adaptations to either dieting or overfeeding than just leptin. Rather, it’s an integrated response involving leptin, insulin, ghrelin, fatty acids, liver, fat cell and skeletal msucle adaptations, and probably factors that haven’t been discovered yet. This probably explains why injecting leptin into dieting humans only reverses some but not all of the adaptations.

For example, just injecting leptin would be expected to fix a defect in TSH (and thyroid output) but it won’t fix the problems with conversion that occur at the liver. Similarly, while injecting leptin would normalize LH and FSH output, it won’t correct the problem with increased binding of testosterone caused by lowered insulin. Hopefully you get the picture. So, you ask, what’s the solution?

The Solution: Cyclical Dieting

Ok, great, I’ve just spent nearly 10 pages making a case for cycling dieting, periods where you alternate a low-calorie intake with a higher calorie intake. in this fashion, you alternate between periods of low calories/carbs with high calories/carbs to alternate between periods of anabolism (tissue building) and catabolism (tissue breakdown). Fundamentally, of course, this is nothing new.

Several years ago, when I first started making some of the connections with leptin and everything else, this really pointed out the need to do periodic refeeds (or cheat days or whatever you want to call them) on a diet. If nothing else, it pointed to another reason why the Bodyopus diet worked as well as it did: by forcefeeding carbs and calories for 2 days, not only did you refill muscle glycogen and hopefully generate an anabolic response, you probably reversed some of the adapatations inhernet to dieting.

In those years, various approaches have come and gone. In general, short refeeds, lasting from 5 to 24 hours were used every so often while dieting. I’ve tried them all. The Bodyopus diet was aimed at this goal, alternating 5 days of low-cal/ketogenic dieting with 2 days of high-carbohdyrate eating. Other approaches such as the Anabolic Diet or Rob Faigan’s Natural Hormonal Enhancement followed roughly the same scheme. There have been numerous other schemes over the years that alternated periods of low and high calories. The question is whether or not those programs were optimal. In my opinion, they aren’t for several reasons.

One of the factors I’ve been considering to a great degree has to do with the length of the overfeeding period. While it’s true that 5 (or 12 or 24) hours of concentrated overfeeding will raise leptin, the more important question is whether that’s sufficient to ‘tell’ the brain that you’re fed. While data (especially in humans) is nonexistent, my hunch is no.

There’s a lag time of several days between the drop in leptin and the drop in metabolic rate (nervous system output) for example; I’d be surprised if a mere 12 or 24 hours was sufficient to reverse this. Rather, I’d expect it to take a similar amount of time for the reversal to occur. The reasons I feel this way are sort of beyond the scope of this book, send me an email if you really must know.

Now, this isn’t to say that short carb-loads/refeeds aren’t of benefit. They refill glycogen, turn off catabolism and maybe induce an anabolic response to boot. They also let you eat some of the crap you’re really craving which helps psychologically. But I doubt they are sufficient to affect metabolism very much. Instead, a longer refeed is necessary. The drawback, of course, is that longer refeeds have a tendency to put too much bodyfat back on which goes agains the entire goal of dieting.

Another problem with many cyclical dieting approaches is that they don’t coordinate training with the diet. Bodyopus was an exception but, for various reasons, I think the Bodyopus workout plan was screwy. If anything it was backwards, putting tension workouts on low-calorie/low-carb days (where you aren’t very anabolic) and glycogen depletion workouts before you are eating a lot seemed wrong to me years ago and wronger to me now. This will make more sense as you read the next chapters.

Ultimately, all of this introductory stuff, brings us to the final question: how do we optimize the entire system to maximize fat loss and either muscle maintenance or muscle gain (or, if you’re a performance athlete, how do we generate fat loss while maintaining performance). To understand that, I need to get into a few more details regarding muscle gain and fat loss, which will help you to understand the overall system.

At a very fundamental level, the problem that natural bodybuilders and athletes have is one of partitioning; that is, where the calories go when you eat more of them or come from when you eat less of them. In an ideal universe, every calorie you ate would go to muscle tissue, with none going into fat cells; you’d gain 100% muscle and no fat. In that same ideal universe, every calorie used during dieting would come from fat stores; you’d lose 100% fat and no muscle. Unfortunately, we don’t live in an ideal universe.

As I mentioned early in this book, some hapless individuals will lose as much as one pound of muscle for every 2-3 pounds of fat that they lose when they diet. Typically, those same individuals will put on about the same amount of fat and muscle when they overfeed. Thus is the balance of the universe maintained. More genetically advantaged individuals tend to put more calories into muscle (meaning less into fat) when they overeat and pull more calories out of fat cells (and less out of muscle) when they diet. They stay naturally lean and have few problems dieting. Once again, you aren’t one of them or you wouldn’t be reading this booklet in the first place.

When talking about partitioning of calories, researchers refer to something called the P-ratio. Essentially, it represents the amount of protein that is either gained (or lost) during over (or under) feeding. So a low P-ratio when dieting would mean you used very little protein and a lot of fat. A high P-ratio would mean that you used a lot of protein and very little fat. It looks like, for the most part, P-ratio is more or less the same for a given individual; as I mentioned above, they will gain about same amount of muscle when they overfeed as they lose when they diet. This is yet another example of the body’s attempts to maintain itself at a ‘normal’ level.

So what controls P-ratio. As depressing as this is, the majority of of the P-ratio is out of our control; it’s mostly genetic. We can control, maybe 15-20% of it with how we eat or train. Supraphysiological amounts of certain compounds (supplements) and, of course, drugs, can also affect the P-ratio.

So what are the main determinants of calorie partitioning? Obviously, hormones are crucially important. High testosterone levels tend to have positive paritioning effects (more muscle, less fat) while chronically high levels of cortisol have the opposite effect (less muscle, more fat). Thyroid and nervous system activity affect not only metabolic rate but also fat burning; optimized thyroid and nervous system levels mean better fat burning, which means less muscle loss when you diet. It also means less fat gain when you overeat. Unfortunately, levels of these hormones are basically ‘set’ by our genetics; the only way to change them significantly is with supplements or drugs. Beyond that, there’s not a whole lot we can do to control them.

Another factor controlling P-ratio is insulin sensitivity which refers to how well or how poorly a given tissue responds to the hormone insulin. Now, insulin is a storage hormone, affecting nutrient storage in tissues such as liver, muscle and fat cells. In that same ideal world, we’d have high insulin sensitivity in skeletal muscle (as this would tend to drive more calories into muscle) and poor insulin sensitivity in fat cells (making it harder to store calories there). This is especially true when you’re trying to gain muscle.

In contrast, when you diet, it’s actually better to be insulin resistant (note that two of the most effective diet drugs, GH and clenbuterol/ephedrine cause insulin resistance). By limiting the muscle’s use of glucose for fuel, you not only spare glucose for use by the brain, but you increase the muscles use of fatty acids for fuel.

In addition to hormonal advantages, it’s likely that the genetic elite have high skeletal muscle insulin sensitivity. They store tremendous amounts of calories in muscle which leaves less to go to fat cells. Their bodies also don’t have to release as much insulin in response to food intake.

In contrast, individuals with poor skeletal muscle insulin sensitivity tend to overproduce insulin, don’t store calories in muscle well (part of why they have trouble getting a pump, poor glycogen storage in muscle cells) and tend to spill calories over to fat cells more effectively.

So what controls insulin sensitivity? As always, a host of factors. One is simply genetic, folks can vary 10 fold in their sensitivity to insulin. Another is diet. Diets high in carbohydrates (especially highly refined carbohydrates), saturated fats and low in fiber tend to impair insulin sensitivity. Diets with lowered carbohydrates (or less refined sources), healthier fats (fish oils, monounsaturated fats like olive oil) and higher fiber intakes invariably improve insulin sensitivity.

Another major factor is activity which influences insulin sensitivity in a number of ways. The first is that muscular contraction itself improves insulin sensitivity, facilitating glucose uptake into the cell. Glycogen depletion (remember this, it’s important) improves insulin sensitivity as well.

So what else controls the P-ratio. As it turns out, the primary predictor of P-ratio during over- and under-feeding is bodyfat percentage. The more bodyfat you carry, the more fat you tend to lose when you diet (meaning less muscle) and the leaner you are, the less fat you tend to lose (meaning more muscle). The same goes in reverse: naturally lean (but NOT folks who have dieted to lean) individuals tend to gain more muscle and less fat when they overfeed and fatter individuals tend to gain more fat and less muscle when they overfeed.

The question is why, why is bodyfat percentage having such a profound impact on P-ratio. Well, there are a few easy answers. One is that bodyfat and insulin sensitivity tend to correlate: the fatter you get, the more insulin resistant you tend to get and the leaner you are the more insulin sensitive you tend to be.

A second is that, the fatter you are, the more fatty acids you have available for fuel. In general, when fatty acids are available in large amounts, they get used. This spares both glucose and protein. By extension, the leaner you get, the more problems you tend to have; as it gets harder to mobilize fatty acids, the body has less to use. This increases the reliance on amino acids (protein) for fuel. The original Ultimate Diet advocated medium chain triglycerides (a special type of fatty acid that is used more easily for fuel than standard fats) and this can be a good strategy under certain circumstances. The newly available DAG oil (http://www.enova.com) might have some use in this regards too.

But that’s not all and it turns out that bodyfat percentage is controlling metabolism to a much greater degree than just by providing fatty acids. Research over the past 10 years or so has identified bodyfat stores as an endocrine tissue in its own right, secreting various hormones and protein that have major effects on other tissues. Perhaps the most important, and certainly the one most talked about is, leptin but that’s far from the only one. Tumor necrosis factor-alpha, the various interleukins, adiponectin and other compounds released from fat cells are sending signals to other tissues in the body which affect metabolism.

Without getting into all of the nitpicky details (many of which haven’t been worked out yet), I just want to talk a little about leptin (if you read my last book, this will all be familiar ground).

Leptin: The Short Course

Leptin is a protein released primarily from fat cells although other tissues such as muscle also contribute slightly. Leptin levels primarily correlate with bodyfat percentage, the more fat you have the more leptin you tend to have (note: different depots of fat, visceral versus subcutaneous, show different relationships with leptin). At any given bodyfat percentage, women typically produce 2-3 times as much leptin as men.

In addition to being related to the amount of bodyfat you have, leptin levels are also related to how much you’re eating. For example, in response to dieting, leptin levels may drop by 50% within a week (or less) although you obviously haven’t lost 50% of your bodyfat. After that initial rapid drop, there is a slower decrease in leptin related to the loss of bodyfat that is occurring. In response to overfeeding, leptin tends to rebound equally quickly. In contrast to what you might think, it looks like leptin production by fat cells is mainly determined by glucose availability (you’d think it was fat intake). So whenever you start pulling glucose out of the fat cell (dieting), leptin levels go down, when you drive glucose into fat cells, it goes up.

Basically, leptin represents two different factors: how much bodfyat you’re carrying, and how much you’re eating. That is, it acts as a signal to the rest of your body about your energy stores. I’ll come back to this in a second.

Like most hormones in the body, leptin has effects on most tissues in the body and leptin receptors have been found all over the place, in the liver, skeletal muscle, in immune cells; you name it and there are probably leptin receptors there. There are also leptin receptors in the brain but I’ll come back to that below. For now, let’s look at a few of the effects that leptin has on other tissues in the body.

In the liver, leptin tends to reduce insulin secretion from the beta-cells. In skeletal muscle, leptin promotes fat burning and tends to spare glucose (and therefore amino acid use). In fat cells, leptin may promote fat oxidation as well as making the fat cell somewhat insulin resistant. Leptin also affects immune cell function, decreasing leptin impairs the body’s ability to mount an immune response. Now you know at least part of the reason you tend to get sick more when you diet. On and on it goes.

Leptin and the Brain

Now, I want you to think back to the first couple of chapters of this book, where I talked about the evolutionary reasons it’s so hard to lose bodyfat. To your body, becoming too lean is a very real threat to your survival. From a physiological standpoint, that means that your body needs a way to ‘know’ how much energy you have stored.

As you may have guessed (or knew from my last booklet), leptin is one of the primary signals (along with many others including ghrelin, insulin, protein YY and god knows what else will turn up) that signals the brain about how much energy you have stored and how much you’re eating.

All of these hormones send an integrated signal to a part of the brain called the hypothalamus that ‘tell’ it what’s going on elsewhere in your body. This causes changes in various neurochemicals such as NPY, CRH, POMC, alpha-MSH and others, to occur. This has a variety of effects (mostly bad) on metabolic rate, hormone levels and nutrient partitioning.

So metabolic rate goes down, levels of thyroid stimulating hormone, leutinizing hormone and follicle stimulating hormone (TSH, LH and FSH respectively) go down meaning lowered levels of thyroid and testosterone, levels of growth hormone releasing hormone (GHRH) go down meaning GH output can be impaired, sympathetic nervous system activity goes down, cortisol levels go up as does hunger and appetite, etc., etc. What you end up seeing is an all purposes systems crash when you try to take bodyfat below a certain level.

I want to point out that falling leptin has a much larger impact on the body’s metabolism than raising leptin does (unless you’re raising it back to normal). That is, the body fights against dieting to a far greater degree than it does overfeeding. This is why, generally speaking, it’s a lot easier to get fat than it is to get lean. Of course, there are exceptions, folks who seem to resist obesity (or weight gain altogether). Research will probably find that they are extremely sensitive to the effects of leptin, so when calories go up, they simply burn off the excess calories without getting fat.

Most of us aren’t that lucky. Rather, like insulin sensitivity discussed above, researchers will probably find that leptin sensitivity is a huge factor influencing how changes in caloric intake affect metabolism. Someone with good leptin sensitivity will tend to stay naturally lean and have an easy time dieting; folks with worse leptin sensitivity (leptin resistance) won’t.

Now, as I pointed out in my last book, injectable leptin is a pipe-dream at this point, an effective dose costing nearly $1000/day (not to mention requiring twice daily injections). Using bromocriptine or other dopamine agonists seemed to fix at least part of the problems by sending a false signal to the brain, making it think leptin levels were normal. Recent studies that have given injectable leptin to dieters show that that fall in leptin is one of the primary signals in initiating the adaptation to dieting. However, unlike in rats, injecting leptin into humans doesn’t fix all of the problems.

This is because, in humans, there is more of an integrated response to both over and underfeeding. To make this easier to understand, let’s look at some of the major things that occur when you cut calories. To understand this better, I want to take a snapshot of what happens when you either reduce or increase calories.

Continued in Calorie Partitioning: Part 2.

For many years (decades?) a common suggestion was that one should attempt to gain some muscle mass mass (through resistance training and possibly overeating) prior to beginning a diet. Well meaning individuals would suggest you spent 3-4 weeks or more training hard and eating well to gain muscle mass. The goal was to raise metabolism so that the diet would go more effectively.

In that current data indicates that each pound of muscle might burn an additional 6 calories (as opposed to older values of 25-40 cal/lb or even higher) (1), this argument is no longer tenable; to significantly affect metabolic rate would require a monstrous gain of muscle mass, far more than you could gain in 3-4 weeks.

Even if you gained 10 pounds of muscle, that would only add up to an additional 60 calories burned per day, hardly enough to worry about and certainly not enough to affect the following diet. Which isn’t to say that diets don’t work better after short or even medium periods of overfeeding, mind you, it’s simply not because of gains in muscle mass.

A more recent idea making the rounds in bodybuilding nutrition is that, prior to trying to gain lean body mass, people should diet down first. This reasoning is based on a variety of data that has examined the changes in body composition that occur when you overfeed either thin or fat individuals (see for example, Reference 2 or just about anything Gilbert Forbes has written over the past 30 years).

A Primer on the P-Ratio

The above recommendation is based on a lot of data on something called the P-ratio (which stands for partitioning ratio) which essentially represents the proportion of protein (LBM) you gain relative to the total weight you gain (this isn’t the technical definition of P-ratio, by the way, I’m just trying to simplify it a bit).

Now, a lot of factors control P-ratio including genetics, hormones, diet and training (to a smaller degree than you’d expect) and probably some I’m forgetting (3). But by and large, the primary predictor of P-ratio is starting body fat percentage. Basically, your starting body fat percentage predicts the great majority of what you will lose/gain when you diet/overfeed (4).

So, when you diet, the fatter you are, the less LBM (and more fat) you will lose. Conversely, the leaner you are, the more LBM and less fat you will tend to lose when you diet. This makes sense in evolutionary terms, the more fat you have to lose, the more your body can lose without having to burn off muscle tissue; the leaner you get, the less fat you have and the more muscle you end up losing. Anyone who’s dieted naturally to sub 10% body fat levels knows this to be true: the leaner you get, the more muscle mass you tend to lose

So what about overfeeding and gaining weight? Well, in general, the same holds but in reverse: leaner individuals will tend to gain more LBM and less fat and fatter individuals will tend to gain more fat and less LBM. This actually makes sense when you think about it. The fat individual loses a lot of fat/a little LBM when they diet and gains a lot of fat and little LBM when they overfeed while the leaner individual does the opposite. P-ratio appears to be constant going in both directions. That is, P-ratio appears to be constant for a given individual (5).

So, typically, when overfed, thin/lean individual will gain 60-70% lean body mass (LBM) while fat individuals may gain only 30-40% LBM. Note that these percentage gains are without exercise, simply with overfeeding from a starting body fat level. Although research hasn’t examined overfeeding nearly as much as underfeeding, we might expect intensive weight training to skew these numbers to an even better point.

So far, so good right; it sure seems like the leaner you are, the better your body composition changes will be during overfeeding? So get lean and then train and eat and you should gain piles of muscle back, right?

The Problem: Naturally Lean People vs. Dieted Down People

The problem with the above analysis, exciting as it sounds, is that there are significant differences between folks who are naturally lean (on whom the original overfeeding research was done) and subjects who have been dieted to leanness.

Let’s consider, for a second the likely physiology of those folks who stay naturally lean. Based on the Geneticcs Hypothesis (3), we’d expect them to have pretty good hormonal status in terms of thyroid levels, low or normal cortisol, maybe decent levels of testosterone, GH and IGF-1. They probably also show a normal nervous system output and an ability to increase fat oxidation when calories are raised as well.

We’d probably expect them to exhibit a spendthrift metabolism (6), one that cranks up in response to overfeeding to burn off excess calories. It wouldn’t be surprising if they were the ones who showed a great deal of Non-Exercise Activity Thermogenesis (NEAT, 7) which is what allows them to burn off excess calories without getting fat. All of this, almost certainly with other factors would all contribute to their general lack of fat gain during overfeeding. Of course, if fat gain is limited during overfeeding, that would tend to mean that any weight gain will tend to be LBM, as the P-ratio data described above indicates.

The problem is that the above physiological profile in no way describes individuals who have dieted down to a low body fat percentage. Rather, dieted individuals typically show a biology that is absolutely not geared towards anything except packing the body fat back on. Typically, the metabolic consequences of dieting include a lowered metabolism, decreased fat oxidation, decreased HSL activity, increased LPL activity impaired hormonal status (including lowered testosterone and raised cortisol), decreased thermogenesis from a reduction in both thyroid levels and nervous system output and a host of other metabolic defects. All of these serve to both slow fat loss during the diet and ensure rapid fat regain when food is reintroduced.

For example, in the classic starvation study (the Minnesota Semi-Starvation study) men were dieted for 6 solid months reaching 4-5% body fat at the end of the study. Then they were refed and body composition was tracked. By the theory being advocated, they should have gained lots of LBM and little fat during refeeding, they were clearly super lean to start out with. But this is absolutely not what happened.

As would be expected based on the metabolic adaptations to dieting, their bodies were mainly primed to replenish fat stores. Reductions in metabolic rate, fat oxidation and thermogenesis all contributed to a preferential gain of body fat and these systems didn’t reset themselves until all of the body fat lost had been regained (8). Quite in fact, signals from body fat (i.e. leptin and the rest) are the mechanism behind this physiology (9).

The bottom line is that, in dieted down individuals, the body is primed to gain body fat at the expense of LBM to replenish what was lost during the diet. Again, this is fundamentally different than looking at genetically lean individuals (for whom a low body fat percentage is their normal level) in terms of what happens when they are overfed.

And even without this research available, anybody who’s dieted to a low body fat percentage can attest to the above. Regardless of the theories being advocated by the individuals looking just at Forbes’ data on P-ratio, the end of the diet is a time when you gain body fat the most easily. Even a brief look at the real world should have pointed out why the theory was incorrect in the first place.

Now Watch me Backpedal a Little

Having hopefully shown you why I think the idea that getting lean first will magically let you pack on the LBM without fat gain, I’m going to backpedal and say that that doesn’t mean I think that dieting first is always a bad idea. Quite in fact, there may be very good reasons to diet prior to going on a mass gaining phase. It’s just not for the reason that many are now advocating.

Part of the reason that preceding a mass gaining phase with a diet is one of practicality. If you want to compete in a bodybuilding contest, you need to be sufficiently lean to start with (10-12% body fat for males) to have a chance of coming in on time. That may mean keeping body fat in check by dieting prior to trying to add mass. Similarly, if you simply want to get lean for appearances sake, you need to keep body fat under control.

Meaning this: if you start a mass gaining phase at too high of a body fat percentage (say 12-15%), you’re going to gain some fat during that phase and end up in the high teens or worse. This makes dieting back to a non-fat assed body fat percentage a real hassle. Better to keep things in check by alternating periods of cutting and gaining.

As well, it seems empirically that once body fat gets to the 15% range or so for men, fat gains tend to accelerate during mass gaining phases. I suspect this is due to the development of systemic insulin resistance which causes calories to go into fat stores more readily. Keeping body fat levels below that may be helpful.

I should mention that there was always an anecdotal idea that mass gains were best with body fat about 10-12% body fat (for men, add 9-12% for women). While I had always dismissed this as being an excuse to stay fat, I suspect it’s probably close to correct. Based on what’s going on hormonally and physiologically at both low and higher body fat percentages, this may very well be a sweet spot for mass gaining. You’re fed and healthy enough to lift well and make gains but not so fat that other problems arise.

Practical Recommendations

Ok, enough theory crap. Based on the above data, here’s what I would generally recommend to bodybuilders or athletes who want to put on muscle mass (i.e. all of them).

1. If you’re above 15% body fat (about 24-27% for women), diet first. If you can get to the 10-12% (19-24%) body fat range or so, I think you’ll be in an overall better position to gain mass. Trying to get super lean will probably end up screwing you in the long run because your body will be primed to put back fat on (and most other physiological systems are screwed up as well) when you get super lean.
2. After finishing your diet, regardless of how lean you get, take 2 weeks to eat at roughly maintenance calorie levels before starting your mass gaining phase. The reason has to do with the physiological adaptations to dieting described briefly above. Although you can’t reverse all of them short of getting fat again (or fixing the problem pharmaceutically), 2 weeks at maintenance, which by definition should be higher calories than you were eating on your diet, will help to normalize some of them. Leptin, thyroid, SNS output should improve a bit, along with other hormones, putting you in a better place to gain mass without super excessive fat gain. Make sure to get at least 100 grams of carbs/day or more during this phase so that thyroid will come back up.
3. Only try to add mass/bulk until you hit the top end body fat percentage listed in #1 above. So that’s about 15% body fat for men and 24-27% body fat for women. What this would mean in practice is that you diet to 10-12% body fat for men (22-24% for women), eat at maintenance for two weeks to try and normalize things, and then add mass until you hit 15% body fat for men (22-24% for women) and then diet back down. Over a number of cycles, you should be able to increase your muscle mass while keeping body fat under control

Summing up:

So there you have it, a look at the impact of initial body fat and how it impacts on changes in body composition. Contrary to current (mis) interpretations of the literature, individuals who have dieted down to low body fat levels don’t magically put on lots of LBM when they gain. Quite in fact, if anything, the opposite is true. After an extended diet, the body is primed for fat gain.

However, that doesn’t mean that dieting prior to a mass-gaining phase is a bad idea and getting reasonbly lean prior to ‘bulking’ is probably the best strategy for the average natural bodybuilder.

References:

1. McClave SA, Snider HL. Dissecting the energy needs of the body. Curr Opin Clin Nutr Metab Care. 2001 Mar;4(2):143-7.
2. Forbes GB. Body fat content influences the body composition response to nutrition and exercise. Ann N Y Acad Sci. (2000) 904:359-65.
3. Bray GA. GENETICSS hypothesis of nutrient partitioning. Progress in Obesity Research:7 (1996) 43-48.
4. Dulloo AG, Jacquet J. The control of partitioning between protein and fat during human starvation: its internal determinants and biological significance. Br J Nutr. (1999) 82:339-56.
5. Dulloo AG. Partitioning between protein and fat during starvation and refeeding: is the assumption of intra-individual constancy of P-ratio valid? Br J Nutr. 1998 Jan;79(1):107-13
6. Weyer C et. al. Changes in energy metabolism in response to 48 h of overfeeding and fasting in Caucasians and Pima Indians. Int J Obes Relat Metab Disord. 2001 May;25(5):593-600.
7. Levine JA. Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science. 1999 Jan 8;283(5399):212-4.
8. Dulloo AG et. al. Autoregulation of body composition during weight recovery in human: the Minnesota Experiment revisited. nt J Obes Relat Metab Disord. 1996 May;20(5):393-405.
9. Dulloo AG, Jacquet J. Adaptive reduction in basal metabolic rate in response to food deprivation in humans: a role for feedback signals from fat stores. Am J Clin Nutr. 1998 Sep;68(3):599-606.