Tuesday, August 31, 2010

How to become diabetic in 6 hours!? Thanks Dr. Delgado for bringing science to the masses!

(Note: My apologies for the sarcastic tone of this post. I am not really congratulating anybody here!)

Dr. Nick Delgado shows us in this YouTube video how to "become diabetic" in 6 hours!

I must admit that I liked the real-time microscope imaging, and wish he had shown us more of that.

But really!

After consulting with my mentor, the MIMIW, I was reminded that there is at least one post on this blog that shows how one can "become diabetic" in just over 60 minutes – that is, about 6 times faster than using the technique described by Dr. Delgado.

The technique used in the post mentioned above is called "intense exercise", which is even believed to be health-promoting! (Unlike drinking olive oil as if it was water, or eating white bread.)

The advantage of this technique is that one can "become diabetic" by doing something healthy!

Thanks Dr. Delgado, your video ranks high up there, together with this Ali G. video, as a fine example of how to bring real science to the masses.

Sunday, August 29, 2010

Heavy physical activity may significantly reduce heart disease deaths, especially after age 45

The idea that heavy physical activity is a main trigger of heart attacks is widespread. Often endurance running and cardio-type activities are singled out. Some people refer to this as “death by running”. Others think that strength training has a higher lethal potential. We know based on the Oregon Sudden Unexpected Death Study that this is a myth.

Here is some evidence that heavy physical activity in fact has a significant protective effect. The graph below, from Brooks et al. (2005) shows the number of deaths from coronary heart disease, organized by age group, in longshoremen (dock workers). The shaded bars represent those whose level of activity at work was considered heavy. The unshaded bars represent those whose level of activity at work was considered moderate or light (essentially below the “heavy” level).

The data is based on an old and classic study of 6351 men, aged 35 to 74 years, who were followed either for 22 years, or to death, or to the age of 75. It shows a significant protective effect of heavy activity, especially after age 45. The numbers atop the unshaded bars reflect the relative risk of death from coronary heart disease in each age group. For example, in the age group 65-74, the risk among those not in the heavy activity group is 110 percent higher (2.1 times higher) than in the heavy activity group.

It should be noted that this is a cumulative effect, of years of heavy activity. Based on the description of the types of activities performed, and the calories spent, I estimate that the heavy activity group performed the equivalent of a few hours of strength training per week, plus a lot of walking and other light physical activities. The authors of the study concluded that “… repeated bursts of high energy output established a plateau of protection against coronary mortality.

Heavy physical activity may not make you lose much weight, but has the potential to make you live longer.


Brooks, G.A., Fahey, T.D., & Baldwin, K.M. (2005). Exercise physiology: Human bioenergetics and its applications. Boston, MA: McGraw-Hill.

Saturday, August 28, 2010

Saturated Fat, Glycemic Index and Insulin Sensitivity: More Evidence

Insulin is a hormone that drives glucose and other nutrients from the bloodstream into cells, among other things. A loss of sensitivity to the insulin signal, called insulin resistance, is a core feature of modern metabolic dysfunction and can lead to type II diabetes and other health problems. Insulin resistance affects a large percentage of people in affluent nations, in fact the majority of people in some places. What causes insulin resistance? Researchers have been trying to figure this out for decades.*

Since saturated fat is blamed for everything from cardiovascular disease to diabetes, it's no surprise that a number of controlled trials have asked if saturated fat feeding causes insulin resistance when compared to other fats. From the way the evidence is sometimes portrayed, you might think it does. However, a careful review of the literature reveals that this position is exaggerated, to put it mildly (1).

The glycemic index, a measure of how much a specific carbohydrate food raises blood sugar, is another common concept in the diet-health literature. On the surface, it makes sense: if excess blood sugar is harmful, then foods that increase blood sugar should be harmful. Despite evidence from observational studies, controlled trials as long as 1.5 years have shown that the glycemic index does not influence insulin sensitivity or body fatness (2, 3, 4). The observational studies may be confounded by the fact that white flour and sugar are the two main high-glycemic foods in most Western diets. Most industrially processed carbohydrate foods also have a high glycemic index, but that doesn't imply that their high glycemic index is the reason they're harmful.

All of this is easy for me to accept, because I'm familiar with examples of traditional cultures eating absurd amounts of saturated fat and/or high-glycemic carbohydrate, and not developing metabolic disease (5, 6, 7). I believe the key is that their food is not industrially processed (along with exercise, sunlight exposure, and probably other factors).

A large new study just published in the American Journal of Clinical nutrition has taken the evidence to a new level (8). At 6 months and 720 participants, it was both the largest and one of the longest studies to address the question. Participants were assigned to one of the following diets:
  1. High saturated fat, high glycemic index
  2. High monounsaturated fat, high glycemic index
  3. High monounsaturated fat, low glycemic index
  4. Low fat, high glycemic index
  5. Low fat, low glycemic index
Compliance to the diets was pretty good. From the nature of the study design, I suspect the authors were expecting participants on diet #1 to fare the worst. They were eating a deadly combination of saturated fat and high glycemic carbohydrate! Well to their dismay, there were no differences in insulin sensitivity between groups at 6 months. Blood pressure also didn't differ between groups, although the low-fat groups lost more weight than the monounsaturated fat groups. The investigators didn't attempt to determine whether the weight loss was fat, lean mass or both. The low-fat groups also saw an increase in the microalbumin:creatinine ratio compared to other groups, indicating a possible deterioration of kidney function.

In my opinion, the literature as a whole consistently shows that if saturated fat or high glycemic carbohydrate influence insulin sensitivity, they do so on a very long timescale, as no effect is detectable in controlled trails of fairly long duration. While it is possible that the controlled trials just didn't last long enough to detect an effect, I think it's more likely that both factors are irrelevant.

Fats were provided by the industrial manufacturer Unilever, and were incorporated into margarines, which I'm sure were just lovely to eat. Carbohydrate was also provided, including "bread, pasta, rice, and cereals." In other words, all participants were eating industrial food. I think these types of investigations may be limited by reductionist thinking. I prefer studies like Dr. Staffan Lindeberg's paleolithic diet trials (9, 10, 11). The key difference? They focus mostly on diet quality, not calories or specific nutrients. And they have shown that quality is king!

* Excess body fat is almost certainly a major cause. When fat mass increases beyond a certain point, particularly abdominal fat, the fat tissue typically becomes inflamed. Inflamed fat tissue secretes factors which reduce whole-body insulin sensitivity (12, 13). The big question is: what caused the fat gain?

Tuesday, August 24, 2010

Lipotoxicity or tired pancreas? Abnormal fat metabolism as a possible precondition for type 2 diabetes

The term “diabetes” is used to describe a wide range of diseases of glucose metabolism; diseases with a wide range of causes. The diseases include type 1 and type 2 diabetes, type 2 ketosis-prone diabetes (which I know exists thanks to Michael Barker’s blog), gestational diabetes, various MODY types, and various pancreatic disorders. The possible causes include genetic defects (or adaptations to very different past environments), autoimmune responses, exposure to environmental toxins, as well as viral and bacterial infections; in addition to obesity, and various other apparently unrelated factors, such as excessive growth hormone production.

Type 2 diabetes and the “tired pancreas” theory

Type 2 diabetes is the one most commonly associated with the metabolic syndrome, which is characterized by middle-age central obesity, and the “diseases of civilization” brought up by Neolithic inventions. Evidence is mounting that a Neolithic diet and lifestyle play a key role in the development of the metabolic syndrome. In terms of diet, major suspects are engineered foods rich in refined carbohydrates and refined sugars. In this context, one widely touted idea is that the constant insulin spikes caused by consumption of those foods lead the pancreas (figure below from Wikipedia) to get “tired” over time, losing its ability to produce insulin. The onset of insulin resistance mediates this effect.

Empirical evidence against the “tired pancreas” theory

This “tired pancreas” theory, which refers primarily to the insulin-secreting beta-cells in the pancreas, conflicts with a lot of empirical evidence. It is inconsistent with the existence of isolated semi/full hunter-gatherer groups (e.g., the Kitavans) that consume large amounts of natural (i.e., unrefined) foods rich in easily digestible carbohydrates from tubers and fruits, which cause insulin spikes. These groups are nevertheless generally free from type 2 diabetes. The “tired pancreas” theory conflicts with the existence of isolated groups in China and Japan (e.g., the Okinawans) whose diets also include a large proportion of natural foods rich in easily digestible carbohydrates, which cause insulin spikes. Yet these groups are generally free from type 2 diabetes.

Humboldt (1995), in his personal narrative of his journey to the “equinoctial regions of the new continent”, states on page 121 about the natives as a group that: "… between twenty and fifty years old, age is not indicate by wrinkling skin, white hair or body decrepitude [among natives]. When you enter a hut is hard to differentiate a father from son …" A large proportion of these natives’ diets included plenty of natural foods rich in easily digestible carbohydrates from tubers and fruits, which cause insulin spikes. Still, there was no sign of any condition that would suggest a prevalence of type 2 diabetes among them.

At this point it is important to note that the insulin spikes caused by natural carbohydrate-rich foods are much less pronounced than the ones caused by refined carbohydrate-rich foods. The reason is that there is a huge gap between the glycemic loads of natural and refined carbohydrate-rich foods, even though the glycemic indices may be quite similar in some cases. Natural carbohydrate-rich foods are not made mostly of carbohydrates. Even an Irish (or white) potato is 75 percent water.

More insulin may lead to abnormal fat metabolism in sedentary people

The more pronounced spikes may lead to abnormal fat metabolism because more body fat is force-stored than it would have been with the less pronounced spikes, and stored body fat is not released just as promptly as it should be to fuel muscle contractions and other metabolic processes. Typically this effect is a minor one on a daily basis, but adds up over time, leading to fairly unnatural patterns of fat metabolism in the long run. This is particularly true for those who lead sedentary lifestyles. As for obesity, nobody gets obese in one day. So the key problem with the more pronounced spikes may not be that the pancreas is getting “tired”, but that body fat metabolism is not normal, which in turn leads to abnormally high or low levels of important body fat-derived hormones (e.g., high levels of leptin and low levels of adiponectin).

One common characteristic of the groups mentioned above is absence of obesity, even though food is abundant and often physical activity is moderate to low. Repeat for emphasis: “… even though food is abundant and often physical activity is moderate to low”. Note that having low levels of activity is not the same as spending the whole day sitting down in a comfortable chair working on a computer. Obviously caloric intake and level of activity among these groups were/are not at the levels that would lead to obesity. How could that be possible? See this post for a possible explanation.

Excessive body fat gain, lipotoxicity, and type 2 diabetes

There are a few theories that implicate the interaction of abnormal fat metabolism with other factors (e.g., genetic factors) in the development of type 2 diabetes. Empirical evidence suggests that this is a reasonable direction of causality. One of these theories is the theory of lipotoxicity.

Several articles have discussed the theory of lipotoxicity. The article by Unger & Zhou (2001) is a widely cited one. The theory seems to be widely based on the comparative study of various genotypes found in rats. Nevertheless, there is mounting evidence suggesting that the underlying mechanisms may be similar in humans. In a nutshell, this theory proposes the following steps in the development of type 2 diabetes:

    (1) Abnormal fat mass gain leads to an abnormal increase in fat-derived hormones, of which leptin is singled out by the theory. Some people seem to be more susceptible than others in this respect, with lower triggering thresholds of fat mass gain. (What leads to exaggerated fat mass gains? The theory does not go into much detail here, but empirical evidence from other studies suggests that major culprits are refined grains and seeds, as well as refined sugars; other major culprits seem to be trans fats, and vegetable oils rich in linoleic acid.)

    (2) Resistance to fat-derived hormones sets in. Again, leptin resistance is singled out as the key here. (This is a bit simplistic. Other fat-derived hormones, like adiponectin, seem to clearly interact with leptin.) Since leptin regulates fatty acid metabolism, the theory argues, leptin resistance is hypothesized to impair fatty acid metabolism.

    (3) Impaired fat metabolism causes fatty acids to “spill over” to tissues other than fat cells, and also causes an abnormal increase in a substance called ceramide in those tissues. These include tissues in the pancreas that house beta-cells, which secrete insulin. In short, body fat should be stored in fat cells (adipocytes), not outside them.

    (4) Initially fatty acid “spill over” to beta-cells enlarges them and makes them become overactive, leading to excessive insulin production in response to carbohydrate-rich foods, and also to insulin resistance. This is the pre-diabetic phase where hypoglycemic episodes happen a few hours following the consumption of carbohydrate-rich foods. Once this stage is reached, several natural carbohydrate-rich foods also become a problem (e.g., potatoes and bananas), in addition to refined carbohydrate-rich foods.

    (5) Abnormal levels of ceramide induce beta-cell apoptosis in the pancreas. This is essentially “death by suicide” of beta cells in the pancreas. What follows is full-blown type 2 diabetes. Insulin production is impaired, leading to very elevated blood glucose levels following the consumption of carbohydrate-rich foods, even if they are unprocessed.

It is widely known that type 2 diabetics have impaired glucose metabolism. What is not so widely known is that usually they also have impaired fatty acid metabolism. For example, consumption of the same fatty meal is likely to lead to significantly more elevated triglyceride levels in type 2 diabetics than non-diabetics, after several hours. This is consistent with the notion that leptin resistance precedes type 2 diabetes, and inconsistent with the “tired pancreas” theory.

Weak and strong points of the theory of lipotoxicity

A weakness of the theory of lipotoxicity is its strong lipophobic tone; at least in the articles that I have read. See, for example, this article by Roger H. Unger in the Journal of the American Medical Association. There is ample evidence that eating a lot of the ultra-demonized saturated fat, per se, is not what makes people obese or type 2 diabetic. Yet overconsumption of trans fats and vegetable oils rich in linoleic acid does seem to be linked with obesity and type 2 diabetes. (So does the consumption of refined grains and seeds, and refined sugars.) The theory of lipotoxicity does not seem to make these distinctions.

In defense of the theory of lipotoxicity, it does not argue that there cannot be thin diabetics. Many type 1 diabetics are thin. Type 2 diabetics can also be thin, even though that is much less common. In certain individuals, the threshold of body fat gain that will precipitate lipotoxicity may be quite low. In others, the same amount of body fat gain (or more) may in fact increase their insulin sensitivity under certain circumstances – e.g., when growth hormone levels are abnormally low.

Autoimmune disorders, perhaps induced by environmental toxins, or toxins found in certain refined foods, may cause the immune system to attack the beta-cells in the pancreas. This may lead to type 1 diabetes if all beta cells are destroyed, or something that can easily be diagnosed as type 2 (or type 1.5) diabetes if only a portion of the cells are destroyed, in a way that does not involve lipotoxicity.

Nor does the theory of lipotoxicity predict that all those who become obese will develop type 2 diabetes. It only suggests that the probability will go up, particularly if other factors are present (e.g., genetic propensity). There are many people who are obese during most of their adult lives and never develop type 2 diabetes. On the other hand, some groups, like Hispanics, tend to develop type 2 diabetes more easily (often even before they reach the obese level). One only has to visit the South Texas region near the Rio Grande border to see this first hand.

What the theory proposes is a new way of understanding the development of type 2 diabetes; a way that seems to make more sense than the “tired pancreas” theory. The theory of lipitoxicity may not be entirely correct. For example, there may be other mechanisms associated with abnormal fat metabolism and consumption of Neolithic foods that cause beta-cell “suicide”, and that have nothing to do with lipotoxicity as proposed by the theory. (At least one fat-derived hormone, tumor necrosis factor-alpha, is associated with abnormal cell apoptosis when abnormally elevated. Levels of this hormone go up immediately after a meal rich in refined carbohydrates.) But the link that it proposes between obesity and type 2 diabetes seems to be right on target.

Implications and thoughts

Some implications and thoughts based on the discussion above are the following. Some are extrapolations based on the discussion in this post combined with those in other posts. At the time of this writing, there were 90 posts on this blog, in addition to many comments. See under "Labels" at the bottom-right area of this blog for a summary of topics addressed. It is hard to ignore things that were brought to light in previous posts.

    - Let us start with a big one: Avoiding natural carbohydrate-rich foods in the absence of compromised glucose metabolism is unnecessary. Those foods do not “tire” the pancreas significantly more than protein-rich foods do. While carbohydrates are not essential macronutrients, protein is. In the absence of carbohydrates, protein will be used by the body to produce glucose to supply the needs of the brain and red blood cells. Protein elicits an insulin response that is comparable to that of natural carbohydrate-rich foods on a gram-adjusted basis (but significantly lower than that of refined carbohydrate-rich foods, like doughnuts and bagels). Usually protein does not lead to a measurable glucose response because glucagon is secreted together with insulin in response to ingestion of protein, preventing hypoglycemia.

    - Abnormal fat gain should be used as a general measure of one’s likelihood of being “headed south” in terms of health. The “fitness” level for men and women shown on the table in this post seem like good targets for body fat percentage. The problem here, of course, is that this is not as easy as it sounds. Attempts at getting lean can lead to poor nutrition and/or starvation. These may make matters worse in some cases, leading to hormonal imbalances and uncontrollable hunger, which will eventually lead to obesity. Poor nutrition may also depress the immune system, making one susceptible to a viral or bacterial  infection that may end up leading to beta-cell destruction and diabetes. A better approach is to place emphasis on eating a variety of natural foods, which are nutritious and satiating, and avoiding refined ones, which are often addictive “empty calories”. Generally fat loss should be slow to be healthy and sustainable.

    - Finally, if glucose metabolism is compromised, one should avoid any foods in quantities that cause an abnormally elevated glucose or insulin response. All one needs is an inexpensive glucose meter to find out what those foods are. The following are indications of abnormally elevated glucose and insulin responses, respectively: an abnormally high glucose level 1 hour after a meal (postprandial hyperglycemia); and an abnormally low glucose level 2 to 4 hours after a meal (reactive hypoglycemia). What is abnormally high or low? Take a look at the peaks and troughs shown on the graph in this post; they should give you an idea. Some insulin resistant people using glucose meters will probably realize that they can still eat several natural carbohydrate-rich foods, but in small quantities, because those foods usually have a low glycemic load (even if their glycemic index is high).

Lucy was a vegetarian and Sapiens an omnivore. We apparently have not evolved to be pure carnivores, even though we can be if the circumstances require. But we absolutely have not evolved to eat many of the refined and industrialized foods available today, not even the ones marketed as “healthy”. Those foods do not make our pancreas “tired”. Among other things, they “mess up” fat metabolism, which may lead to type 2 diabetes through a complex process involving hormones secreted by body fat.


Humboldt, A.V. (1995). Personal narrative of a journey to the equinoctial regions of the new continent. New York, NY: Penguin Books.

Unger, R.H., & Zhou, Y.-T. (2001). Lipotoxicity of beta-cells in obesity and in other causes of fatty acid spillover. Diabetes, 50(1), S118-S121.

Thursday, August 19, 2010

Tropical Plant Fats: Coconut Oil, Part II

Heart Disease: Animal Studies

Although humans aren't rats, animal studies are useful because they can be tightly controlled and experiments can last for a significant portion of an animal's lifespan. It's essentially impossible to do a tightly controlled 20-year feeding study in humans.

The first paper I'd like to discuss come from the lab of Dr. Thankappan Rajamohan at the university of Kerala (1). Investigators fed three groups of rats different diets:
  1. Sunflower oil plus added cholesterol
  2. Copra oil, a coconut oil pressed from dried coconuts, plus added cholesterol
  3. Freshly pressed virgin coconut oil, plus added cholesterol
Diets 1 and 2 resulted in similar lipids, while diet 3 resulted in lower LDL and higher HDL. A second study also showed that diet 3 resulted in lower oxidized LDL, a dominant heart disease risk factor (2). Overall, these papers showed that freshly pressed virgin coconut oil, with its full complement of "minor constituents"*, partially protects rats against the harmful effects of cholesterol overfeeding. These are the only papers I could find on the cardiovascular effects of unrefined coconut oil in animals!

Although unrefined coconut oil appears to be superior, even refined coconut oil isn't as bad as it's made out to be. For example, compared to refined olive oil, refined coconut oil protects against atherosclerosis (hardening and thickening of the arteries) in a mouse model of coronary heart disease (LDL receptor knockout). In the same paper, coconut oil caused more atherosclerosis in a different mouse model (ApoE knockout) (3). So the vascular effects of coconut oil depend in part on the animals' genetic background.

In general, I've found that the data are extremely variable from one study to the next, with no consistent trend showing refined coconut oil to be protective or harmful relative to refined monounsaturated fats (like olive oil) (4). In some cases, polyunsaturated oils cause less atherosclerosis than coconut oil in the context of an extreme high-cholesterol diet because they sometimes lead to blood lipid levels that are up to 50% lower. However, even this isn't consistent across experiments. Keep in mind that atherosclerosis is only one factor in heart attack risk.

What happens if you feed coconut oil to animals without adding cholesterol, and without giving them genetic mutations that promote atherosclerosis? Again, the data are contradictory. In rabbits, one investigator showed that serum cholesterol increases transiently, returning to baseline after about 6 months, and atherosclerosis does not ensue (5). A different investigator showed that coconut oil feeding results in lower blood lipid oxidation than sunflower oil (6). Yet a study from the 1980s showed that in the context of a terrible diet composition (40% sugar, isolated casein, fat, vitamins and minerals), refined coconut oil causes elevated blood lipids and atherosclerosis (7). This is almost certainly because overall diet quality influences the response to dietary fats in rabbits, as it does in other mammals.

Heart Disease: Human Studies

It's one of the great tragedies of modern biomedical research that most studies focus on nutrients rather than foods. This phenomenon is called "nutritionism". Consequently, most of the studies on coconut oil used a refined version, because the investigators were most interested in the effect of specific fatty acids. The vitamins, polyphenols and other minor constituents of unrefined oils are eliminated because they are known to alter the biological effects of the fats themselves. Unfortunately, any findings that result from these experiments apply only to refined fats. This is the fallacy of the "X fatty acid does this and that" type statements-- they ignore the biological complexity of whole foods. They would probably be correct if you were drinking purified fatty acids from a beaker.

Generally, the short-term feeding studies using refined coconut oil show that it increases both LDL ("bad cholesterol") and HDL ("good cholesterol"), although there is so much variability between studies that it makes firm conclusions difficult to draw (8, 9). As I've written in the past, the ability of saturated fats to elevate LDL appears to be temporary; both human and certain animal studies show that it disappears on timescales of one year or longer (10, 11). That hasn't been shown specifically for coconut oil that I'm aware of, but it could be one of the reasons why traditional cultures eating high-coconut diets don't have elevated serum cholesterol.

Another marker of cardiovascular disease risk is lipoprotein (a), abbreviated Lp(a). This lipoprotein is a carrier for oxidized lipids in the blood, and it correlates with a higher risk of heart attack. Refined coconut oil appears to lower Lp(a), while refined sunflower oil increases it (12).

Unfortunately, I haven't been able to find any particularly informative studies on unrefined coconut oil in humans. The closest I found was a study from Brazil showing that coconut oil reduced abdominal obesity better than soybean oil in conjunction with a low-calorie diet, without increasing LDL (13). It would be nice to have more evidence in humans confirming what has been shown in rats that there's a big difference between unrefined and refined coconut oil.

Coconut Oil and Body Fat

In addition to the study mentioned above, a number of experiments in animals have shown that "medium-chain triglycerides", the predominant type of fat in coconut oil, lead to a lower body fat percentage than most other fats (14). These findings have been replicated numerous times in humans, although the results have not always been consistent (15). It's interesting to me that these very same medium-chain saturated fats that are being researched as a fat loss tool are also considered by mainstream diet-heart researchers to be among the most deadly fatty acids.

Coconut Oil and Cancer

Refined coconut oil produces less cancer than seed oils in experimental animals, probably because it's much lower in omega-6 polyunsaturated fat (16, 17). I haven't seen any data in humans.

The Bottom Line

There's very little known about the effect of unrefined coconut oil on animal and human health, however what is published appears to be positive, and is broadly consistent with the health of traditional cultures eating unrefined coconut foods. The data on refined coconut oil are conflicting and frustrating to sort through. The effects of refined coconut oil seem to depend highly on dietary context and genetic background. In my opinion, virgin coconut oil can be part of a healthy diet, and may even have health benefits in some contexts.

* Substances other than the fat itself, e.g. vitamin E and polyphenols. These are removed during oil refining.

The theory of supercompensation: Strength training frequency and muscle gain

Moderate strength training has a number of health benefits, and is viewed by many as an important component of a natural lifestyle that approximates that of our Stone Age ancestors. It increases bone density, muscle mass, and improves a number of health markers. Done properly, it may decrease body fat percentage.

Generally one would expect some muscle gain as a result of strength training. Men seem to be keen on upper-body gains, while women appear to prefer lower-body gains. Yet, many people do strength training for years, and experience little or no muscle gain.

Paradoxically, those people experience major strength gains, both men and women, especially in the first few months after they start a strength training program. However, those gains are due primarily to neural adaptations, and come without any significant gain in muscle mass. This can be frustrating, especially for men. Most men are after some noticeable muscle gain as a result of strength training. (Whether that is healthy is another story, especially as one gets to extremes.)

After the initial adaptation period, of “beginner” gains, typically no strength gains occur without muscle gains.

The culprits for the lack of anabolic response are often believed to be low levels of circulating testosterone and other hormones that seem to interact with testosterone to promote muscle growth, such as growth hormone. This leads many to resort to anabolic steroids, which are drugs that mimic the effects of androgenic hormones, such as testosterone. These drugs usually increase muscle mass, but have a number of negative short-term and long-term side effects.

There seems to be a better, less harmful, solution to the lack of anabolic response. Through my research on compensatory adaptation I often noticed that, under the right circumstances, people would overcompensate for obstacles posed to them. Strength training is a form of obstacle, which should generate overcompensation under the right circumstances. From a biological perspective, one would expect a similar phenomenon; a natural solution to the lack of anabolic response.

This solution is predicted by a theory that also explains a lack of anabolic response to strength training, and that unfortunately does not get enough attention outside the academic research literature. It is the theory of supercompensation, which is discussed in some detail in several high-quality college textbooks on strength training. (Unlike popular self-help books, these textbooks summarize peer-reviewed academic research, and also provide the references that are summarized.) One example is the excellent book by Zatsiorsky & Kraemer (2006) on the science and practice of strength training.

The figure below, from Zatsiorsky & Kraemer (2006), shows what happens during and after a strength training session. The level of preparedness could be seen as the load in the session, which is proportional to: the number of exercise sets, the weight lifted (or resistance overcame) in each set, and the number of repetitions in each set. The restitution period is essentially the recovery period, which must include plenty of rest and proper nutrition.

Note that toward the end there is a sideways S-like curve with a first stretch above the horizontal line and another below the line. The first stretch is the supercompensation stretch; a window in time (e.g., a 20-hour period). The horizontal line represents the baseline load, which can be seen as the baseline strength of the individual prior to the exercise session. This is where things get tricky. If one exercises again within the supercompensation stretch, strength and muscle gains will likely happen. (Usually noticeable upper-body muscle gain happens in men, because of higher levels of testosterone and of other hormones that seem to interact with testosterone.) Exercising outside the supercompensation time window may lead to no gain, or even to some loss, of both strength and muscle.

Timing strength training sessions correctly can over time lead to significant gains in strength and muscle (see middle graph in the figure below, also from Zatsiorsky & Kraemer, 2006). For that to happen, one has not only to regularly “hit” the supercompensation time window, but also progressively increase load. This must happen for each muscle group. Strength and muscle gains will occur up to a point, a point of saturation, after which no further gains are possible. Men who reach that point will invariably look muscular, in a more or less “natural” way depending on supplements and other factors. Some people seem to gain strength and muscle very easily; they are often called mesomorphs. Others are hard gainers, sometimes referred to as endomorphs (who tend to be fatter) and ectomorphs (who tend to be skinnier).

It is not easy to identify the ideal recovery and supercompensation periods. They vary from person to person. They also vary depending on types of exercise, numbers of sets, and numbers of repetitions. Nutrition also plays a role, and so do rest and stress. From an evolutionary perspective, it would seem to make sense to work all major muscle groups on the same day, and then do the same workout after a certain recovery period. (Our Stone Age ancestors did not do isolation exercises, such as bicep curls.) But this will probably make you look more like a strong hunter-gatherer than a modern bodybuilder.

To identify the supercompensation time window, one could employ a trial-and-error approach, by trying to repeat the same workout after different recovery times. Based on the literature, it would make sense to start at the 48-hour period (one full day of rest between sessions), and then move back and forth from there. A sign that one is hitting the supercompensation time window is becoming a little stronger at each workout, by performing more repetitions with the same weight (e.g., 10, from 8 in the previous session). If that happens, the weight should be incrementally increased in successive sessions. Most studies suggest that the best range for muscle gain is that of 6 to 12 repetitions in each set, but without enough time under tension gains will prove elusive.

The discussion above is not aimed at professional bodybuilders. There are a number of factors that can influence strength and muscle gain other than supercompensation. (Still, supercompensation seems to be a “biggie”.) Things get trickier over time with trained athletes, as returns on effort get progressively smaller. Even natural bodybuilders appear to benefit from different strategies at different levels of proficiency. For example, changing the workouts on a regular basis seems to be a good idea, and there is a science to doing that properly. See the “Interesting links” area of this web site for several more focused resources of strength training.


Zatsiorsky, V., & Kraemer, W.J. (2006). Science and practice of strength training. Champaign, IL: Human Kinetics.

Wednesday, August 18, 2010

Tropical Plant Fats: Coconut Oil, Part I

Traditional Uses for Coconut

Coconut palms are used for a variety of purposes throughout the tropics. Here are a few quotes from the book Polynesia in Early Historic Times:
Most palms begin to produce nuts about five years after germination and continue to yield them for forty to sixty years at a continuous (i.e., nonseasonal) rate, producing about fifty nuts a year. The immature nut contains a tangy liquid that in time transforms into a layer of hard, white flesh on the inner surface of the shell and, somewhat later, a spongy mass of embryo in the nut's cavity. The liquid of the immature nut was often drunk, and the spongy embryo of the mature nut often eaten, raw or cooked, but most nuts used for food were harvested after the meat had been deposited and before the embryo had begun to form...

After the nut had been split, the most common method of extracting its hardened flesh was by scraping it out of the shell with a saw-toothed tool of wood, shell, or stone, usually lashed to a three-footed stand. The shredded meat was then eaten either raw or mixed with some starchy food and then cooked, or had its oily cream extracted, by some form of squeezing, for cooking with other foods or for cosmetic or medical uses...

Those Polynesians fortunate enough to have coconut palms utilized their components not only for drink and food-- in some places the most important, indeed life-supporting food-- but also for building-frames, thatch, screens, caulking material, containers, matting, cordage, weapons, armor, cosmetics, medicine, etc.
Mainstream Ire

Coconut fat is roughly 90 percent saturated, making it one of the most highly saturated fats on the planet. For this reason, it has been the subject of grave pronouncements by health authorities over the course of the last half century, resulting in its near elimination from the industrial food system. If the hypothesis that saturated fat causes heart disease and other health problems is correct, eating coconut oil regularly should tuck us in for a very long nap.

Coconut Eaters

As the Polynesians spread throughout the Eastern Pacific islands, they encountered shallow coral atolls that were not able to sustain their traditional starchy staples, taro, yams and breadfruit. Due to its extreme tolerance for poor, salty soils, the coconut palm was nearly the only food crop that would grow on these islands*. Therefore, their inhabitants lived almost exclusively on coconut and seafood for hundreds of years.

One group of islands that falls into this category is Tokelau, which fortunately for us was the subject of a major epidemiological study that spanned the years 1968 to 1982: the Tokelau Island Migrant Study (1). By this time, Tokelauans had managed to grow some starchy foods such as taro and breadfruit (introduced in the 20th century by Europeans), as well as obtaining some white flour and sugar, but their calories still came predominantly from coconut.

Over the time period in question, Tokelauans obtained roughly half their calories from coconut, placing them among the most extreme consumers of saturated fat in the world. Not only was their blood cholesterol lower than the average Westerner, but their hypertension rate was low, and physicians found no trace of previous heart attacks by ECG (age-adjusted rates: 0.0% in Tokelau vs 3.5% in Tecumseh USA). Migrating to New Zealand and cutting saturated fat intake in half was associated with a rise in ECG signs of heart attack (1.0% age-adjusted) (2, 3).

Diabetes was low in men and average in women by modern Western standards, but increased significantly upon migration to New Zealand and reduction of coconut intake (4). Non-migrant Tokelauans gained body fat at a slower rate than migrants, despite higher physical activity in the latter (5). Together, this evidence seriously challenges the idea that coconut is unhealthy.

The Kitavans also eat an amount of coconut fat that would make Dr. Ancel Keys blush. Dr. Staffan Lindeberg found that they got 21% of their 2,200 calories per day from fat, nearly all of which came from coconut. They were getting 17% of their calories from saturated fat; 55% more than the average American. Dr. Lindeberg's detailed series of studies found no trace of coronary heart disease or stroke, nor any obesity, diabetes or senile dementia even in the very old (6, 7).

Of course, the Tokelauans, Kitavans and other traditional cultures were not eating coconut in the form of refined, hydrogenated coconut oil cake icing. That distinction will be important when I discuss what the biomedical literature has to say in the next post.

* Most also had pandanus palms, which are also tolerant of poor soils and whose fruit provided a small amount of starch and sugar.

Friday, August 13, 2010

The evolution of costly traits: Competing for women can be unhealthy for men

There are human traits that evolved in spite of being survival handicaps. These counterintuitive traits are often called costly traits, or Zahavian traits (in animal signaling contexts), in honor of the evolutionary biologist Amotz Zahavi (Zahavi & Zahavi, 1997). I have written a post about this type of traits, and also an academic article (Kock, 2009). The full references and links to these publications are at the end of this post.

The classic example of costly trait is the peacock’s train, which is used by males to signal health to females. (Figure below from: animals.howstuffworks.com.) The male peacock’s train (often incorrectly called “tail”) is a costly trait because it impairs the ability of a male to flee predators. It decreases a male’s survival success, even though it has a positive net effect on the male’s reproductive success (i.e., the number of offspring it generates). It is used in sexual selection; the females find big and brightly colored trains with many eye spots "sexy".

So costly traits exist in many species, including the human species, but we have not identified them all yet. The implication for human diet and lifestyle choices is that our ancestors might have evolved some habits that are bad for human survival, and moved away from others that are good for survival. And I am not only talking about survival among modern humans; I am talking about survival among our human ancestors too.

The simple reason for the existence of costly traits in humans is that evolution tends to maximize reproductive success, not survival, and that applies to all species. (Inclusive fitness theory goes a step further, placing the gene at the center of the selection process, but this is a topic for another post.) If that were not the case, rodent species, as well as other species that specialize in fast reproduction within relatively short life spans, would never have evolved.

Here is an interesting piece of news about research done at the University of Michigan. (I have met the lead researcher, Dan Kruger, a couple of times at HBES conferences. My impression is that his research is solid.) The research illustrates the evolution of costly traits, from a different angle. The researchers argue, based on the results of their investigation, that competing for a woman’s attention is generally bad for a man’s health!

Very romantic ...


Kock, N. (2009). The evolution of costly traits through selection and the importance of oral speech in e-collaboration. Electronic Markets, 19(4), 221-232.

Zahavi, A. & Zahavi, A. (1997). The Handicap Principle: A missing piece of Darwin’s puzzle. Oxford, England: Oxford University Press.

Thursday, August 12, 2010

Can a Statin Neutralize the Cardiovascular Risk of Unhealthy Dietary Choices?

The title of this post is the exact title of a recent editorial in the American Journal of Cardiology (1). Investigators calculated the "risk for cardiovascular disease associated with the total fat and trans fat content of fast foods", and compared it to the "risk decrease provided by daily statin consumption". Here's what they found:
The risk reduction associated with the daily consumption of most statins, with the exception of pravastatin, is more powerful than the risk increase caused by the daily extra fat intake associated with a 7-oz hamburger (Quarter Pounder®) with cheese and a small milkshake. In conclusion, statin therapy can neutralize the cardiovascular risk caused by harmful diet choices.

Routine accessibility of statins in establishments providing unhealthy food might be a rational modern means to offset the cardiovascular risk. Fast food outlets already offer free condiments to supplement meals. A free statin-containing accompaniment would offer cardiovascular benefits, opposite to the effects of equally available salt, sugar, and high-fat condiments. Although no substitute for systematic lifestyle improvements, including healthy diet, regular exercise, weight loss, and smoking cessation, complimentary statin packets would add, at little cost, 1 positive choice to a panoply of negative ones.
Wow. Later in the editorial, they recommend "a new and protective packet, “MacStatin,” which could be sprinkled onto a Quarter Pounder or into a milkshake." I'm not making this up!

I can't be sure, but I think there's a pretty good chance the authors were being facetious in this editorial, in which case I think a) it's hilarious, b) most people aren't going to get the joke. If they are joking, the editorial is designed to shine a light on the sad state of mainstream preventive healthcare. Rather than trying to educate people and change the deadly industrial food system, which is at the root of a constellation of health problems, many people think it's acceptable to partially correct one health risk by tinkering with the human metabolism using drugs. To be fair, most people aren't willing to change their diet and lifestyle habits (and perhaps for some it's even too late), so frustrated physicians prescribe drugs to mitigate the risk. I accept that. But if our society is really committed to its own health and well-being, we'll remove the artificial incentives that favor industrial food, and educate children from a young age on how to eat well.

I think one of the main challenges we face is that our current system is immensely lucrative for powerful financial interests. Industrial agriculture lines the pockets of a few large farmers and executives (while smaller farmers go broke and get bought out), industrial food processing concentrates profit among a handful of mega-manufacturers, and then people who are made ill by the resulting food spend an exorbitant amount of money on increasingly sophisticated (and expensive) healthcare. It's a system that effectively milks US citizens for a huge amount of money, and keeps the economy rolling at the expense of the average person's well-being. All of these groups have powerful lobbies that ensure the continuity of the current system. Litigation isn't the main reason our healthcare is so expensive in the US; high levels of chronic disease, expensive new technology, a "kitchen sink" treatment approach, and inefficient private companies are the real reasons.

If the editorial is serious, there are so many things wrong with it I don't even know where to begin. Here are a few problems:
  1. They assume the risk of heart attack conveyed by eating fast food is due to its total and trans fat content, which is simplistic. To support that supposition, they cite one study: the Health Professionals Follow-up Study (2). This is one of the best diet-health observational studies conducted to date. The authors of the editorial appear not to have read the study carefully, because it found no association between total or saturated fat intake and heart attack risk, when adjusted for confounding variables. The number they quoted (relative risk = 1.23) was before adjustment for fiber intake (relative risk = 1.02 after adjustment), and in any case, it was not statistically significant even before adjustment. How did that get past peer review? Answer: reviewers aren't critical of hypotheses they like.
  2. Statins mostly work in middle-aged men, and reduce the risk of heart attack by about one quarter. The authors excluded several recent unsupportive trials from their analysis. Dr. Michel de Lorgeril reviewed these trials recently (3). For these reasons, adding a statin to fast food would probably have a negligible effect on the heart attack risk of the general population.
  3. "Statins rarely cause negative side effects." BS. Of the half dozen people I know who have gone on statins, all of them have had some kind of negative side effect, two of them unpleasant enough that they discontinued treatment against their doctor's wishes. Several of them who remained on statins are unlikely to benefit because of their demographic, yet they remain on statins on their doctors' advice.
  4. Industrial food is probably the main contributor to heart attack risk. Cultures that don't eat industrial food are almost totally free of heart attacks, as demonstrated by a variety of high-quality studies (4, 5, 6, 7, 8, 9). No drug can replicate that, not even close.
I have an alternative proposal. Rather than giving people statins along with their Big Mac, why don't we change the incentive structure that artificially favors the Big Mac, french fries and soft drink? If it weren't for corn, soybean and wheat subsidies, fast food wouldn't be so cheap. Neither would any other processed food. Fresh, whole food would be price competitive with industrial food, particularly if we applied the grain subsidies to more wholesome foods. Grass-fed beef and dairy would cost the same as grain-fed. I'm no economist, so I don't know how realistic this really is. However, my central point still stands: we can change the incentive structure so that it no longer artificially favors industrial food. That will require that the American public get fed up and finally butt heads with special interest groups.

Tuesday, August 10, 2010

Nonexercise activities like fidgeting may account for a 1,000 percent difference in body fat gain! NEAT eh?

Some studies become classics in their fields and yet are largely missed by the popular media. This seems to be what happened with a study by Levine and colleagues (1999; full reference and link at the end of this post), which looked at the role that nonexercise activity thermogenesis (NEAT) plays in fat gain suppression. Many thanks go to Lyle McDonald for posting on this.

You have probably seen on the web claims that overeating leads to fat loss, because overeating increases one’s basal metabolic rate. There are also claims that food has a powerful thermic effect, due to the energy needed for digestion, absorption and storage of nutrients; this is also claimed to lead to fat loss. There is some truth to these claims, but the related effects are very small compared with the effects of NEAT.

Ever wonder why there are some folks who seem to eat whatever they want, and never get fat? As it turns out, it may be primarily due to NEAT!

NEAT is associated with fidgeting, maintenance of posture, shifting position, pacing, and other involuntary light physical activities. The main finding of this study was that NEAT accounted for a massive amount of the difference in body fat gain among the participants in the study. The participants were 12 males and 4 females, ranging in age from 25 to 36 years. These healthy and lean participants were fed 1,000 kilocalories per day in excess of their weight-maintenance requirements, for a period of 8 weeks. See figure below; click on it to enlarge.

Fat gain varied more than 10-fold among the participants (or more than 1,000 percent), ranging from a gain of only 0.36 kg (0.79 lbs) to a gain of 4.23 kg (9.33 lbs). As you can see, NEAT explains a lot of the variance in the fat gain variable, which is indicated by the highly statistically significant negative correlation (-0.77). Its effect dwarfs those related to basal metabolic rate and food-induced thermogenesis, neither of which was statistically significant.

How can one use this finding in practice? This research indirectly suggests that moving often throughout the day may have a significant additive long term effect on fat gain suppression. It is reasonable to expect a similar effect on fat loss. And this effect may be stealthy enough to prevent the body from reacting to fat loss by significantly lowering its basal metabolic rate. (Yes, while the increase in basal metabolic rate is trivial in response to overfeeding, the decrease in this rate is nontrivial in response to underfeeding. Essentially the body is much more “concerned” about starving than fattening up.)

The bad news is that it is not easy to mimic the effects of NEAT through voluntary activities. The authors of the study estimated that the maximum increase in NEAT detected in the study (692 kcal/day) would be equivalent to a 15-minute walk every waking hour of every single day! (This other study focuses specifically on fidgeting.) Clearly NEAT has a powerful effect on weight loss, which is not easy to match with voluntary pacing, standing up etc. Moreover, females seem to benefit less from NEAT, because they seem to engage in fewer NEAT-related activities than men. The four lowest NEAT values in the study corresponded to the four female participants.

Nevertheless, if you have a desk job, like I do, you may want to stand up and pace for a few seconds every 30 minutes. You may also want to stand up while you talk on the phone. You may want to shift position from time to time; e.g., sitting at the edge of the chair for a few minutes every hour, without back support. And so on. These actions may take you a bit closer to the lifestyle of our Paleolithic ancestors, who were not sitting down motionless the whole day. Try also eating more like they did and, over a year, the results may be dramatic!


James A. Levine, Norman L. Eberhardt, Michael D. Jensen (1999). Role of nonexercise activity thermogenesis in resistance to fat gain in humans. Science, 283(5399), 212-214.

Saturday, August 7, 2010

Cortisol, surprise-enhanced cognition, and flashbulb memories: Scaring people with a snake screen and getting a PhD for it!

Cortisol is a hormone that has a number of important functions. It gets us out of bed in the morning, it cranks up our metabolism in preparation for intense exercise, and it also helps us memorize things and even learn. Yes, it helps us learn. Memorization in particular, and cognition in general, would be significantly impaired without cortisol. When you are surprised, particularly with something unpleasant, cortisol levels increase and enhance cognition. This is in part what an interesting study suggests; a study in which I was involved. The study was properly “sanctified” by the academic peer-review process (Kock et al., 2009; full reference and link at the end of this post).

The main hypothesis tested through this study is also known as the “flashbulb memorization” hypothesis. Interestingly, up until this study was conducted no one seemed to have used evolution to provide a basis on which flashbulb memorization can be explained. The basic idea here is that enhanced cognition within the temporal vicinity of animal attacks (i.e., a few minutes before and after) allowed our hominid ancestors to better build and associate memories related to the animals and their typical habitat markers (e.g., vegetation, terrain, rock formations), which in turn increased their survival chances. Their survival chances increased because the memories helped them avoid a second encounter; if they survived the first, of course. And so flashbulb memorization evolved. (In fact, it might have evolved earlier than at the hominid stage, and it may also have evolved in other species.)

The study involved 186 student participants. The participants were asked to review web-based learning modules and subsequently take a test on what they had learned. Data from 6 learning modules in 2 experimental conditions were contrasted. In the treatment condition a web-based screen with a snake in attack position was used to surprise the participants; the snake screen was absent in the control condition. See schematic figure below (click on it to enlarge). The “surprise zone” in the figure comprises the modules immediately before and after the snake screen (modules 3 and 4); those are the modules in which higher scores were predicted.

The figure below (click on it to enlarge) shows a summary of the results. The top part of the figure shows the percentage differences between average scores obtained by participants in the treatment and control conditions. The bottom part of the figure shows the average scores obtained by participants in both conditions, as well as the scores that the participants would have obtained by chance. The chance scores would likely have been the ones obtained by the participants if their learning had been significantly impaired for any of the modules; this could have happened due to distraction, for example. As you can see, the scores for all modules are significantly higher than chance.

In summary, the participants who were surprised with the snake screen obtained significantly higher scores for the two modules immediately before (about 20 percent higher) and after (about 40 percent higher) the snake screen. The reason is that the surprise elicited by the snake screen increased cortisol levels, which in turn improved learning for modules 3 and 4. Adrenaline and noradrenaline (epinephrine and norepinephrine) may also be involved. This phenomenon is so odd that it seems to defy the laws of physics; note that Module 3 was reviewed before the snake screen. And, depending on the size of a test, this could have turned a “C” into an “A” grade!

Similarly, it is because of this action of cortisol that Americans reading this post, especially those who lived in the East Coast in 2001, remember vividly where they were, what they were doing, and who they were with, when they first heard about the September 11, 2001 Attacks. I was living in Philadelphia at the time, and I remember those details very vividly, even though the Attacks happened almost 10 years ago. That is one of the fascinating things that cortisol does; it instantaneously turns short-term contextual memories temporally associated with a surprise event (i.e., a few minutes before and after the event) into vivid long-term memories.

This study was part of the PhD research project of one of my former doctoral students, and now Dr. Ruth Chatelain-Jardon. Her PhD was granted in May 2010. She expanded the study through data collection in two different countries, and a wide range of analyses. (It is not that easy to get a PhD!) Her research provides solid evidence that flashbulb memorization is a real phenomenon, and also that it is a human universal. Thanks are also due to Dr. Jesus Carmona, another former doctoral student of mine who worked on a different PhD research project, but who also helped a lot with this project.


Kock, N., Chatelain-Jardón, R., & Carmona, J. (2009). Scaring them into learning!? Using a snake screen to enhance the knowledge transfer effectiveness of a web interface. Decision Sciences Journal of Innovative Education, 7(2), 359-375.

Thursday, August 5, 2010

Saturated Fat Consumption Still isn't Associated with Heart Attack Risk

The American Journal of Clinical Nutrition just published the results of a major Japanese study on saturated fat intake and cardiovascular disease (1). Investigators measured dietary habits, then followed 58,453 men and women for 14.1 years. They found that people who ate the most saturated fat had the same heart attack risk as those who ate the least*. Furthermore, people who ate the most saturated fat had a lower risk of stroke than those who ate the least. It's notable that stroke is a larger public health threat in Japan than heart attacks.

This is broadly consistent with the rest of the observational studies examining saturated fat intake and cardiovascular disease risk. A recent review paper by Dr. Ronald Krauss's group summed up what is obvious to any unbiased person who is familiar with the literature, that saturated fat consumption doesn't associate with heart attack risk (2). In a series of editorials, some of his colleagues attempted to discredit and intimidate him after its publication (3, 4). No meta-analysis is perfect, but their criticisms were largely unfounded (5, 6).

*Actually, people who ate the most saturated fat had a lower risk but it wasn't statistically significant.

Wednesday, August 4, 2010

The baffling rise in seasonal allergies: Global warming or obesity?

The July 26, 2010 issue of Fortune has an interesting set of graphs on page 14. It shows the rise of allergies in the USA, together with figures on lost productivity, doctor visits, and medical expenditures. (What would you expect? This is Fortune, and money matters.) It also shows some cool maps with allergen concentrations, and how they are likely to increase with global warming. (See below; click on it to enlarge; use the "CRTL" and "+" keys to zoom in, and CRTL" and "-" to zoom out.)

The implication: A rise in global temperatures is causing an increase in allergy cases. Supposedly the spring season starts earlier, with more pollen being produced overall, and thus more allergy cases.


I checked their numbers against population growth, because as the population of a country increases, so will the absolute number of allergy cases (as well as cancer cases, and cases of almost any disease). What is important is whether there has been an increase in allergy rates, or the percentage of the population suffering from allergies. Well, indeed, allergy rates have been increasing.

Now, I don’t know about your neck of the woods, but temperatures have been unusually low this year in South Texas. Global warming may be happening, but given recent fluctuations in temperature, I am not sure global warming explains the increases in allergy rates. Particularly the spike in allergy rates in 2010; this seems to be very unlikely to be caused by global warming.

And I have my own experience of going from looking like a seal to looking more like a human being. When I was a seal (i.e., looked like one), I used to have horrible seasonal pollen allergies. Then I lost 60 lbs, and my allergies diminished dramatically. Why? Body fat secretes a number of pro-inflammatory hormones (see, e.g., this post, and also this one), and allergies are essentially exaggerated inflammatory responses.

So I added obesity rates to the mix, and came up with the table and graph below (click on it to enlarge).

Obesity rates and allergies do seem to go hand in hand, don’t you think? The correlation between obesity and allergy rates is a high 0.87!

Assuming that this correlation reflects reasonably well the relationship between obesity and allergy rates (something that is not entirely clear given the small sample), obesity would still explain only 75.7 percent of the variance in allergy rates (this number is the correlation squared). That is, about 24.3 percent of the variance in allergy rates would be due to other missing factors.

A strong candidate for missing factor is something that makes people obese in the first place, namely consumption of foods rich in refined grains, seeds, and sugars. Again, in my experience, removing these foods from my diet reduced the intensity of allergic reactions, but not as much as losing a significant amount of body fat. We are talking about things like cereals, white bread, doughnuts, pasta, pancakes covered with syrup, regular sodas, and fruit juices. Why? These foods also seem to increase serum concentrations of pro-inflammatory hormones within hours of their consumption.

Other candidates are vitamin D levels, and lack of exposure to natural environments during childhood, just to name a few. People seem to avoid the sun like the plague these days, which can lower their vitamin D levels. This is a problem because vitamin D modulates immune responses; so it is important in the spring, as well as in the winter. The lack of exposure to natural environments during childhood may make people more sensitive to natural allergens, like pollen.

Sunday, August 1, 2010

Growth hormone, insulin resistance, body fat accumulation, and glycogen depletion: Making sense of a mysterious hormone replacement therapy outcome

Hormone replacement therapies are prescribed in some cases, for medical reasons. They usually carry some risks. The risks come in part from the body down-regulating its own production of hormones when hormones are taken orally or injected. This could be seen as a form of compensatory adaptation, as the body tries to protect itself from abnormally high hormone levels.

More often than not the down-regulation can be reversed by interrupting the therapy. In some cases, the down-regulation becomes permanent, leading to significant health deterioration over the long run. One can seriously regret having started the hormone replacement therapy in the first place. The same is true (if not more) for hormone supplementation for performance enhancement, where normal hormone secretion levels are increased to enhance (mostly) athletic performance.

Rosenfalck and colleagues (1999) conducted an interesting study linking growth hormone (GH) replacement therapy with insulin resistance. Their conclusions are not very controversial. What I find interesting is what their data analysis unveiled and was not included in their conclusions. Also, they explain their main findings by claiming that there was a deterioration of beta cell function. (Beta cells are located in the pancreas, and secrete insulin.) While they may be correct, their explanation is not very plausible, as you will see below.

Let us take a quick look at what past research says about GH therapy and insulin resistance. One frequent finding is a significant but temporary impairment of insulin sensitivity, which usually normalizes after a period of a few months (e.g., 6 months). Another not so frequent finding is a significant and permanent impairment of insulin sensitivity; this is not as frequent in healthy individuals.

The researchers did a good job at reviewing this literature, and concluded that in many cases GH therapy is not worth the risk. They also studied 24 GH-deficient adults (18 males and 6 females). All of them had known pituitary pathology, which caused the low GH levels. The participants were randomly assigned to two groups. One received 4 months treatment with biosynthetic GH daily (n=13); the other received a placebo (n=11).

The table below (click on it to enlarge) shows various measures before and after treatment. Note the significant reduction in abdominal fat mass in the GH group. Also note that, prior to the treatment, the GH group folks (who were GH-deficient) were overall much heavier and much fatter, particular at the abdominal area, than the folks in the placebo (or control) group.

From the measures above one could say that the treatment was a success. But the researchers point out that it was not, because insulin sensitivity was significantly impaired. They show some graphs (below), and that is where things get really interesting, but not in the way intended by the researchers.

On the figure above, the graphs on the left refer to the placebo group, and on the right to the GH group. The solid lines reflect pre-treatment numbers and dotted lines post-treatment numbers. Indeed, GH therapy is making the GH-deficient folks significantly more insulin resistant.

But look carefully. The GH folks are more insulin sensitive than the controls prior to the treatment, even though they are much fatter, particularly in terms of abdominal fat. The glucose response is significantly lower for the GH-deficient folks, and that is not due to them secreting more insulin. The insulin response is also significantly lower. This is confirmed by glucose and insulin “area under the curve” measures provided by the researchers.

In fact, after treatment both groups seem to have generally the same insulin and glucose responses. This means that the GH treatment made insulin-sensitive folks a bit more like their normal counterparts in the placebo group. But obviously the change for the worse occurred only in the GH group, which is what the researchers concluded.

Now to the really interesting question, at least in my mind: What could have improved insulin sensitivity in the GH-deficient group prior to the treatment?

The GH-deficient folks had more body fat, particularly around the abdominal area. High serum GH is usually associated with low body fat, particularly around the abdominal area, because high GH folks burn it easily. So, looking at it from a different perspective, the GH-deficient folks seem to have been more effective at making body fat, and less effective at burning it.

Often we talk about insulin sensitivity as though there was only one type. But there is more than one type of insulin sensitivity. Insulin signals to the liver to take up glucose from the blood and turn it into glycogen or fat. Insulin also signals to body fat tissue to take up glucose from the blood and make fat with it. (GLUT 4 is an insulin-sensitive glucose transporter present in both fat and muscle cells.)

Therefore, it is reasonable to assume that folks with fat cells that are particularly insulin-sensitive would tend to make body fat quite easily based on glucose. While this is a type of insulin sensitivity that most people probably do not like to have, it may play an important role in reducing blood glucose levels under certain conditions. This appears to be true in the short term. Down the road, having very insulin-sensitive fat cells seems to lead to obesity, the metabolic syndrome, and diabetes.

In fact, in individuals without pituitary pathology, increased insulin sensitivity in fat cells could be a compensatory adaptation in response to a possible decrease in liver and muscle glucose uptake. Lack of exercise will shift the burden of glucose clearance to tissues other than liver and muscle, because with glycogen stores full both liver and muscle will usually take up much less blood glucose than they would otherwise.

I am speculating here, but I think that in individuals without pituitary pathology, an involuntary decrease in endogenous GH secretion may actually be at the core of this compensatory adaptation mechanism. In these individuals, low GH levels may be an outcome, not a cause of problems. This would explain two apparently contradictory findings: (a) GH levels drop dramatically in the 40s, particularly for men; and (b) several people in their 50s and 60s, including men, have much higher levels of circulating GH than people in their 40s, and even than much younger folks.

Vigorous exercise increases blood glucose uptake, inside and outside the exercise window; this is an almost universal effect among humans. Exercise depletes muscle and liver glycogen. (Fasting and low-carbohydrate dieting alone deplete liver, but not muscle, glycogen.) As glycogen stores become depleted, the activity of glycogen synthase (an enzyme involved in the conversion of glucose to glycogen) increases acutely. This activity remains elevated for several days in muscle tissue; the liver replenishes its glycogen in a matter of hours. With glycogen synthase activity elevated, glucose is quickly used to replenish glycogen stores, and not to make fat.

Depleting glycogen stores on a regular basis (e.g., once every few days) may over time reverse the adaptations that made fat cells particularly insulin-sensitive in the first place. Those adaptations become a protection that is not only no longer needed but also detrimental to health, since they lead to obesity. This could be the reason why many people initially find it difficult to lower their body fat set point, but once they lose body fat and stay lean for a while, they seem to become able to maintain their leanness without much effort.

Well, perhaps glycogen-depleting exercise is more important than many people think. It can help make you thin, but through a circuitous path.

And, incidentally, glycogen-depleting exercise causes a temporary but dramatic spike in GH secretion. This natural increase in GH secretion does not seem to be associated with any significant impairment in overall insulin sensitivity, even though glycogen-depleting exercise increases blood glucose levels a lot during the exercise window. This is a temporary and physiological, not pathological, phenomenon.


Rosenfalck A.M., Fisker, S., Hilsted, J., Dinesen, B., Vølund, A., Jørgensen, J.O., Christiansen, J.S., & Madsbad, S. (1999). The effect of the deterioration of insulin sensitivity on beta-cell function in growth-hormone-deficient adults following 4-month growth hormone replacement therapy. Growth Hormone & IGF Research, 9(2), 96–105.