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Research Review Schenk S et. al. Different glycemic indexes of breakfast cereals are not due to glucose entry into blood but to glucose removal by tissue. Am J Clin Nutr. (2003) 78(4):742-8. BACKGROUND: The glycemic index (GI) of a food is thought to directly reflect the rate of digestion and entry of glucose into the systemic circulation. The blood glucose concentration, however, represents a balance of both the entry and the removal of glucose into and from the blood, respectively. Such direct quantification of the postprandial glucose curve with respect to interpreting the GI is lacking in the literature. OBJECTIVE: We compared the plasma glucose kinetics of low- and high-GI breakfast cereals. DESIGN: On 2 occasions, plasma insulin concentrations and plasma glucose kinetics (by constant-rate infusion of [6,6-(2)H(2)]glucose) were measured in 6 healthy males for 180 min after they fasted overnight and then consumed an amount of corn flakes (CF) or bran cereal (BC) containing 50 g available carbohydrate. RESULTS: The GI of CF was more than twice that of BC (131.5 +/- 33.0 compared with 54.5 +/- 7.2; P < 0.05), despite no significant differences in the rate of appearance of glucose into the plasma during the 180-min period. Postprandial hyperinsulinemia occurred earlier with BC than with CF, resulting in a 76% higher plasma insulin concentration at 20 min (20.4 +/- 4.5 compared with 11.6 +/- 2.1 micro U/mL; P < 0.05). This was associated with a 31% higher rate of disappearance of glucose with BC than with CF during the 30-60-min period (28.7 +/- 3.1 compared with 21.9 +/- 3.1 micro mol. kg(-)(1). min(-)(1); P < 0.05). CONCLUSION: The lower GI of BC than of CF was not due to a lower rate of appearance of glucose but instead to an earlier postprandial hyperinsulinemia and an earlier increase in the rate of disappearance of glucose, which attenuated the increase in the plasma glucose concentration. My comments: This is another older paper that I wanted to talk about since it ties in somewhat with the feedback on milk below. In way of introduction, I should probably define glycemic index (GI) for readers who aren't familiar with it. The GI is used to rate carbohydrates by examining the blood glucose response to 50 grams of digestible carbohydrates. After fasting, subjects are first given some reference food; this used to be glucose but researchers now use white bread. The blood glucose response to white bread is defined as 100. Then, the test food is given and the blood glucose response is measured and compared to that of the test food. A food that shows 60% of the blood glucose response to white bread is given a GI of 60. It has commonly been assumed that GI and insulin response are related and bodybuilders and athletes commonly use GI to determine which foods are or are not acceptable to eat (especially on a fat loss diet). Low GI foods are usually assumed to digest slowly and it is the slow rate of glucose into the bloodstream which causes the low GI. A massive number of foods have been tested for GI although there is still much debate as to the validity of GI in meal planning. GI can vary significantly by food and how it is prepared, as well as between individuals. Also, GI is measured for 50 gram quantities of foods (that's 50 grams of digestible carbohydrates). But this can be misleading; for example, carrots are very high on the GI scale but few people would eat 50 grams of digestible carbohydrates worth of carrots in a sitting. To counter this, some researchers have proposed a measure called the glycemic load (GL) which is the total amount of digestible carbohydrate multiplied by the GI. This at least recognizes that, in the real world, carbohydrate intake varies. GL can be lowered by either picking lower GI foods or by eating less total carbohydrate, or some combination of the two. Additionally, GI tends to be affected by other nutrients (protein, fat and fiber) although not always in the way you'd think (and not all research finds a significant impact of protein and fat). For example, protein tends to lower the GI of carbohydrates but insulin levels often increase when you add protein to carbs. For reference, the most complete site on the web for information about GI is Rick Mendosa's Site Which brings us to the above study. As mentioned above, bodybuilders and athletes usually assume that a low GI means a low insulin response but the study above draws that conclusion into question. Rather it found that the low GI food showed a lower blood glucose response because it generated a higher early insulin response (clearing blood glucose out of the bloodstream) at the 30 minute mark (by 60 minutes, both foods showed similar insulin levels). Quoting directly from the paper "BC has a low GI because a more rapid insulin-medited increase in tissue glucose uptake attenuates the increase in blood glucose concentration, despite a similar rate of glucose entry into the blood." That is to say, both foods released glucose into the bloodstream at similar rates, but the bran cereal showed faster uptake due to a higher initial insulin spike, which lowered the overall GI response. The researchers also noted that the bran cereal contained more protein than the corn flakes and this is probably what caused the higher insulin response (and lower blood glucose) which ties into my comments above. Somehow, I don't think bodybuilders would argue that combining low GI carbs with protein is bad for fat loss, yet here we have an (as of yet unreplicated paper) showing that the initial insulin response is higher; essentially, the higher initial insulin response caused the lower GI in this case. Yet most bodybuilders also believe that high insulin is detrimental to fat loss. Here we have a study that I think questions that idea. At the very least, the small initial insulin spike certainly wouldn't appear to be hurting things, it's likely that sustained insulin levels would be more problematic by limiting the ability to mobilize fat for fuel. Then again, at least one study found that spiking insulin (high GI condition) resulted in a larger rebound in blood fatty acid levels (after blood glucose crashed) compared to keeping insulin low but stable (low GI condition) so maybe there's more to this picture than we yet realize. I'll talk about that study in a later newsletter. You can read the full text here.
Feature Article Muscle and Fat: A Primer
In this piece, I want to talk generally about fat and muscle, the roles they play in the body, and the importance that they both have. Most people think of bodyfat as BAD in an absolute sense. If they could get rid of all of their bodyfat, they'd be happy. They'd be dead, mind you, but they'd be happy. Many people (athletes and bodybuilders) tend to think of muscle as GOOD in an absolute sense. A lot of non-athletes (women moreso than men typically) think of muscle as BAD. This is, of course, a vast oversimplification. Let's try to unsimplify it a bit. Fat Let's get fat out of the way first. Here I'm talking about the fat on your body, not the fat in your food. Fat played a crucial role in our survival in the 10,000 odd years before food become regularly available. Acting as a storehouse for energy (and quite a good one at that), excess bodyfat allowed us to survive to the point we are at now: killing ourselves slowly with our modern environment. Even the leanest individual, with a paltry 5 pounds of fat has enough stored energy (17,500 calories give or take) to run 175 miles straight before it's all gone. Most people have a lot more than 5 pounds of fat. In the past, these stored calories allowed people to survive times when there was no food. When food might be unavailable throughout the winter, having an excessive storehouse of energy was a necessity for survival. Being lean thousands of years ago was a definite way not to survive. The folks who survived were the people who could store calories easily to get through the winter. In modern times, with some very rare exceptions, excess bodyfat is simply a health risk. It correlates with increased risk of many diseases including heart disease, stroke, cancer and others. Odd as it may sound, substances released from your enlarged fat cells (such as interleukin-6 and tumor necrosis factor-alpha) are involved in these diseases. The excess bodyweight puts a stress on the joints which have to carry it around and on the heart which has to pump blood to feed it. A particular kind of fat, called visceral fat has even worse metabolic effects and has been implicated in a lot of diseases including insulin resistance syndrome (which is a step down the path to Type II diabetes). But at the same time that too much bodyfat is definitely harmful, too little can be just as unhealthy. First and foremost, there is a small amount of essential fat, surrounding our spinal cords and internal organs. This represents roughly 3% of the total bodyfat in men, 9-12% in women. Our brain contains quite a bit of fat. So do the membranes that make up all of the cells in our body (which are made up of both phospholipids and cholesterol). This is why low-fat diets are harmful to babies, they need the fat to build critical tissues in their bodies, especially their brains. Get rid of too much bodyfat and it's possible to cause actual damage to these tissues. This usually doesn't happen except under the most extreme circumstances such as long term starvation or anorexia but it is possible. Some studies link a lack of brain essential fatty acids (EFA's) to psychosis and depression. As well, and perhaps more importantly, bodyfat plays a crucial role in glucose disposal in the body. Folks who are born without bodyfat (a disease called lipodystrophy) or who lose it for various reasons run into problems with high blood glucose (similar to what is seen in Type II diabetes). On and on it goes. The point being that too little bodyfat can be just as bad as too much. Fat provides insulation to keep you warm in cold environments (very lean individuals tend to be somewhat cold most of the time although some of this is related to metabolic rate crashing). Of course, you can just bundle up more if need be so that's usually not a problem in modern society. Fat also acts as a physical cushion, a crude type of protection. Very lean individuals tend to be uncomfortable sitting for a long time because their bony asses don't provide any cushioning. Athletes involved in impact sports like football may actually benefit from a little extra bodyfat since it dissipates some of the impact of another large object hitting you at a high speed. Studies show that the fat overlying a man's stomach and a woman's hips and thighs is different (more saturated which makes it harder) from the rest of the fat on their body, presumably for a protective reason. Excessively low bodyfat levels, as occurs in competition bodybuilders or high level athletes, can wreck hormonal balance in both males and females. Women's menstrual cycles stop when bodyfat gets too low (the actual reason this occurs is more complicated than low bodyfat per se but this will do for now), indicating that estrogen is very low. This can cause bone loss which is very bad down the road. In men, too little bodyfat can cause testosterone levels to drop to castrate levels and they can't get an erection. What's the point in having the perfect body if you can't use it for anything fun? The point I'm trying to make is that with the exceptions of individuals who must lower bodyfat to extremely low levels, some balance between too little and too much is going to be the best choice from a health and performance standpoint. Muscle: Aesthetic aspects So let's talk about muscle. I'm distinguishing muscle here from the more general LBM component of body composition. Just remember that LBM includes muscle mass, organs, bones, brains, etc. Everything that's not fat, basically. Muscle is one component of LBM, the one that we have the most control over. If you ask someone what they think about muscle, the answer you get depends on the person, and especially their gender. Men tend to think of muscle from a very macho standpoint. Young males want to be big and muscular, or look like Arnold (no last name needed) because that's what they think women want them to look like. Ironically, when you ask women, most find extreme muscularity to be a turnoff although they tend to like men who keep in shape and are fit and healthy (and have a nice butt). On a related note, when asked about body image, the image that women think men want is usually a lot skinnier than what men indicate they actually want. In general, men don't want women who are twigs, but women think that they do. Basically, we all have a screwed up idea of what the physical ideal actually is. Older males have typically lost the urge to look like Arnold, becoming more concerned with health and wellness and maybe losing the extra few pounds of flab that are accumulating around the belly. Older females have roughly the same concept or are more concerned with bone health as they get older. A lot of women seem to fear muscle on their own bodies. Statements of "I want to tone up but I don't want to gain any muscle." are common among personal training clients. Trainers hear it a lot and it gets old fast. This is typically a knee-jerk reaction to the extreme muscularity that is presented in the media of professional female (and male) bodybuilders. What women (and men for that matter) need to realize is that the extreme level of muscle seen in professional bodybuilders can only be achieved with the combination of incredible genetics, years of intensive training, and the use of anabolic drugs. The average woman, training on the average training program doesn't have the capacity to build such muscle. For that matter, neither does the average male. This is a truly ironic thing: males are trying their damnedest to get huge and failing miserably at it, yet women think a little weight training will turn them into a huge muscle-woman overnight. Just shows you how skewed reality and perception tend to be. Muscle: non-aesthetic issues I don't want to just talk about the aesthetics of muscle. Your aesthetics are your own choice. But muscle is critical for a lot of reasons other than to look buffed and get you dates. Let's look at some of them. Older individuals frequently lose the ability to fend for themselves as a consequence of muscle loss. This age related muscle loss (called sarcopenia) forces many to be reliant on others to do the simplest of tasks, such as getting up from a chair. Regular weight training throughout a person's life is probably one of the single most important things they can do to avoid such a fate. Even then, studies of 90 year olds show that even small amounts of weight training increase strength and muscle mass significantly and can give older individuals their self-sufficiency back. So it doesn't look like it's ever too late. Even those who aren't particularly old can have problems with some daily tasks of living if they don't possess adequate muscular strength and size. Carrying large grocery bags, picking up a small child, taking a full recycle bin to the curb all require more strength than a lot of people have in today's world. This includes men and women. Tales of men blowing out their backs picking up their child are not uncommon, but are indicative of just how weak we are as a society. Adding muscle mass and strength through proper weight training can help to deal with that. There is also typically a drop in metabolic rate with age, which causes an accumulation of bodyfat. This drop is most likely caused by the loss of muscle mass. While some of this loss is certainly age-related, some of it is simply a function of decreased activity. That is, as folks become less active with age, they lose muscle, which forces them to be even less active, and the cycle begins. Muscle is also important in health. To get a bit ahead, muscle is made up of amino acids, which can be mobilized in times of stress (i.e. sickness). If you lose too much muscle (as happens in wasting diseases such as cancer and AIDS), your body loses its ability to cope with stress. If you lose 30% of your muscle mass or so, you will die. One of the most often claimed benefits of muscle is that it burns calories; to be specific, muscle is responsible for about 25% of your total energy expenditure. Only your brain and heart use more energy on a per weight basis. Unfortunately, adding muscle to your body doesn't have nearly the potential to increase metabolic rate as we once thought. One pound of muscle may burn an additional 6 calories or so at rest, in contrast to previously claimed values of 10-40 (up to an absurd 100). For reference, a pound of fat burns about 3 cal/lb so the difference really isn't that much. So even adding 10 pounds of muscle is unlikely to impact on resting metabolic rate very much. Most of the metabolic impact of muscle (in terms of weight/fat control) probably has to do with the energy cost of the workouts and what's used to synthesize the muscle tissue. At least some of the drop in metabolic rate when you diet is due to lost muscle tissue although that's far from the whole story. Any decrease in bodymass will lower the number of calories you burn at rest and during exercise; there is an additional adaptive component to metabolic rate drop related to hormones (leptin, thyroid, insulin and nervous system output). You might be surprised to find out that part of the post-diet hunger is related to muscle mass loss (a lot more of it is related to the fat loss but that's life). Given the same fat loss, if you lose more muscle, you'll be hungrier when you end the diet, and more likely to regain the weight. That's on top of the reduction in metabolic rate. I told you your body hated you, now you're starting to see why. For those who are insulin resistant (if you are, you know the term, if you're not you may not but I'll talk about it more later), more muscle mass can increase insulin sensitivity simply because the same amount of insulin has more muscle mass to 'work' on. Regular weight training (necessary to increase muscle mass) also improves insulin sensitivity through a variety of mechanisms that we'll talk about later. Altogether too many weight/fat loss diets don't pay sufficient attention to the maintenance (or rebuilding) of muscle. Whether it's through a lack of exercise or the proper exercise or (especially) inadequate protein intakes, most diets accept muscle/LBM losses as part of the price of losing fat. There is some truth to this but that doesn't mean we have to accept it quietly without fuss. With a very few exceptions, usually involving very obese individuals for whom a loss of actual muscle may be necessary to achieve a healthy weight, or athletes who need to drop muscle for some reason or another, losing muscle mass on a diet is a negative which should be avoided, or at least minimized. A few years ago I would have said that it is always a negative but there are some exceptions and I can't speak in absolutes here. My point being that, no matter what your attitude towards muscle, it is crucial not only for survival and health but for the long-term success of your body recomposition efforts. You may not want or need to gain any more muscle than you have now, and that's fine, but unless you are one of the few weird exceptions, you should do everything in your power to at least prevent muscle loss whether on a diet or due to aging.
Questions and Answers Q: If someone is looking to reduce body fat and is not showing progress at 20% below their calorie maintenance level, what would be the next logical step to induce fat loss? This person engages in regular aerobic and resistance training. A: First, I would ask if this person had just started their diet program. I have repeatedly seen a weird delay in fat loss when a program is first started, this is especially true for women. They'll be doing 'everything right' and little to nothing will happen for the first few weeks. And then, sometime after week 4, there will be a big change in body composition seemingly overnight. There seems to be an initial lag time to get fat loss moving, I'm honestly not sure why. It may be a water thing, it may have to do with the error bar in caliper measurements, it may have to do with gene expression, it may simply be voodoo magic. As a second comment, realize that all of the estimation equations for maintenance intakes are only that, estimations. While 10-12 cal/lb (or an approximate 20% reduction from a baseline of 14-16 cal/lb) are usually sufficient, I have known people who had to go to 8 cal/lb to effectively lose fat. So if this person is reducing 20% from an estimated maintenance, it may still have them too high to lose fat effectively. Because their estimated maintenance is actually lower than the equation predicts. If the individual in question is female, an additional issue is changes in water balance (which can overwhelm true measures of fat loss) through the menstrual cycle. Trying to track fat loss every week or two against changes in water balance can be a futile endeavor, females may need to measure once/month (ideally at the same time point in the menstrual cycle) to get any kind of consistent or comparative measurements. With that said, if someone had been at 20% below predicted maintenance for a month with no actual change in bodyfat, my first suggestion would be to reduce calories further (or increase activity) to generate an additional 10% caloric deficit. They would stay there for 2-4 weeks to assess further progress. If nothing was happening at that point, I'd suggest getting some blood work done to check hormone levels (especially thyroid). Q: As far as low carb diets are concerned, I get the impression from your "tone" lately that ketosis is unnecessary. Is this impression valid? Since you wrote a book on it, what are your thoughts now in 2006. I even get the impression that moderate carb diets are just as effective. Are all the SKD, CKD, TKD's just more awkward diets that automatically lower calories and make you pay attention to what you eat. I have had success with each and the reason I like ketosis is that it is really a no brainer. (Meat, fat, repeat...carb load once in a while.) Please put forth your most recent conclusions, thanks! ps-I body-build, not powerlift or dance ballet! A: Given adequate dietary protein in the first place, I'm not convinced that ketosis is terribly beneficial from either a muscle loss or fat loss standpoint. There's no doubt in my mind that ketosis and the adaptations to it are protein sparing during starvation when protein is insufficient. But given adequate dietary protein on a diet (1-1.5 g/lb lean body mass), I'm no longer convinced. Certainly I don't think that the effect is that pronounced. The impact of ketosis on appetite suppression is debatable as well. Whether the loss of appetite that occurs in people on a low-carb diet (and this isn't universal in the first place) is related to ketosis itself, or due to the increase in dietary protein (the most filling nutrient) or fat (which slows gastric emptying) is arguable. Perhaps it's due to a stabilization of blood glucose; this effect tends to be more pronounced in people who are insulin resistant. I have seen a recent comment in a paper somewhere indicating that ketones may do some interesting things to brain sensors of appetite (AMPk in this case) so this issue is still unresolved in my mind. I'd say that more people than not see a decrease in spontaneous food intake on low-carbohydrate diets (in one study, food intake dropped by 1000 cal/day in diabetics) but for those who don't, it's very easy to overeat due to the high fat content of a typical ketogenic diet. Additionally, the most recent study (cited in the newsletter a while back) comparing a ketogenic to non-ketogenic diet at controlled calorie intakes and with similar protein showed no real benefit to the ketogenic diet over a moderate carb diet (essentially a Zone diet). The controlled calorie intake/identical protein thing is important, most of the work showing ketogenic diets to have a benefit are relying on self-reported food intakes (which are notoriously inaccurate) and the protein intakes tend to vary a lot (which raises questions of whether the carbohydrate intake or protein intake per se is having the major effect). Which isn't to say that keto diets may not have other advantages. As you mention, some people really prefer keto/low-carb diets b/c of their simplicity and they are a no-brainer diet for many people. Eating piles of lean protein, some veggies and reasonable amounts of healthy fats is about as simple as it gets. Throw in some carbs/protein around training and you have a very workable diet. Of course, even there people can screw it up, especially if they gorge on dietary fat (this tends to be more common in non-athletic keto diets like Atkins). I suspect that one reason that they work so well for many people is that they remove many of the classic diet breaker foods (starchy carbs) for some people. When I had success with Bodyopus so many years ago, I'd say that was the primary benefit (in hindsight): it was easier for me to either eat zero carbs (during the week) or tons of carb (carb-load) than to eat moderate amounts. Now I find that I'm happier (feel better, training goes better) on moderate carb diets but it's taken me a while to get to where I could do that kind of a diet and maintain calorie control. Lowering carbs significantly, to near keto-levels, can also be beneficial in mobilizing stubborn bodyfat. So there may be benefits to low-carb diets when people get to the last bit of bodyfat. As an additional and somewhat tangential issue, I have seen people become so concerned with the development of ketosis (or lack thereof) that they miss the goal of the diet: losing bodyfat. You can lose bodyfat effectively and never be in ketosis, and you can be in ketosis and not lose bodyfat. Lean individuals don't go into ketosis as reliably as fatter individuals so chasing ketosis per se is, IMO, a mistake. You can always get into deep ketosis by lowering protein and gorging on dietary fat (especially MCT) but I don't think that's a good strategy for lean athletes trying to maintain LBM during a diet. If it occurs, that's fine; if it doesn't, that's probably fine too. My stance at this point is that ketosis is probably not very relevant given such things as adequate dietary protein and weight training. In the Ultimate diet 2.0 I even addressed this directly with a section called "What about ketosis?" At the 1.5-2 g/lb lean body mass recommended in that book, ketosis probably won't develop. But neither is it important to the success of the diet. To quote what I wrote in that book: "For the most part, I simply see ketosis as a "side-effect" of fat loss (burning to be more accurate), more than something to be explicitly sought out. That is, when you accelerate fat oxidation with the methods above, you tend to enter ketosis. Ketosis in and of itself isn't any big deal. " Q: How do you make a beginner's powerlifting routine? A: A total beginner has three primary goals when it comes to training (whether powerlifting or otherwise)
For a total beginning trainee, I would want them to get as much quality practice on the powerlifts themselves (squat, bench, deadlift) as they can tolerate. This would mean using a high frequency of training for each lift (ideally 3X/week if not more) using submaximal loads. The focus must be on learning proper technique. There's no point piling weight onto the movements before the person can do it properly. I would use a 5X5 pyramid starting light (with the bar) and adding weight gradually. The focus would be on perfect form on every repetition. It might be 6-8 weeks before the person had even basic competency in the lifts, going too heavy too soon will simply impair motor learning so I would keep the weights comfortable (but they would get progressively heavier as technique improved). Initially, all three powerlifts would be trained at each session in the order of squat, bench press, deadlift. As the lifts got heavier, the deadlift would be trained less frequently (every other workout or once/week). Quite honestly, the simplest beginner PL routine would be to do squat, bench, deadlift for 5 sets of 5 three times per week. This doesn't leave much unhit but nor does it hit everything that might be needed. Along with the technique work, a progressive amount of general strengthening work for upper and lower body would be performed. This would be done in a higher repetition range (10-12 for the first 3-4 weeks, moving to 6-8 reps after that) This would serve a number of different purposes
So a basic full body powerlifting workout might be Squat: 5X5 Bench: 5X5 Deadlift: 2-3X5 (you should already be warmed up from the squat) To be honest, after squat and deadlift, not a whole lot more lower body would be needed. For upper body, a second chest exercise (incline or DB press) might be used, some type of row or pulldown for back (these movements could be alternated workout to workout), and perhaps some shoulder (especially rear delt) and arm work. Also, ab and low-back work would be a good idea to begin strengthening the core. Weighted crunches and back extensions would be good here. The supplementary stuff would be done for a couple of sets apiece initially, moving up to 3 sets after the first 4 weeks. Over the course of the first 6-8 weeks of training, the goal would be to gradually increase the weights being handled in the three main lifts, on to of gaining general strength (and size). At this point, a more traditional type of powerlifting split might be done with two lower body days (one squat, one deadlift with assistance work) and two upper body days (bench + extra work). I'd suggest that anyone interested in beginner (moving to intermediate and advanced) strength training routines look up any of Glenn Pendlay's excellent work on the web. The book Starting Strength (which I cannot too highly recommend) also has some good ideas for beginner programming. |
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