Sunday, February 28, 2010

Body fat and disease: How much body fat can I lose in one day?

Body fat is not an inert deposit of energy. It can be seen as a distributed endocrine organ. Body fat cells, or adipocytes, secrete a number of different hormones into the bloodstream. Major hormones secreted by adipose tissue are adiponectin and leptin.

Estrogen is also secreted by body fat, which is one of the reasons why obesity is associated with infertility. (Yes, abnormally high levels of estrogen can reduce fertility in both men and women.) Moreover, body fat secretes tumor necrosis factor-alpha, a hormone that is associated with generalized inflammation and a number of diseases, including cancer, when in excess.

The reduction in circulating tumor necrosis factor-alpha and other pro-inflammatory hormones as one loses weight is one reason why non-obese people usually experience fewer illness symptoms than those who are obese in any given year, other things being equal. For example, the non-obese will have fewer illness episodes that require full rest during the flu season. In those who are obese, the inflammatory response accompanying an illness (which is necessary for recovery) will often be exaggerated.

The exaggerated inflammatory response to illness often seen in the obese is one indication that obesity in an unnatural state for humans. It is reasonable to assume that it was non-adaptive for our Paleolithic ancestors to be unable to perform daily activities because of an illness. The adaptive response would be physical discomfort, but not to the extent that one would require full rest for a few days to fully recover.

Inflammation markers such as C-reactive protein are positively correlated with body fat. As body fat increases, so does inflammation throughout the body. Lipid metabolism is negatively affected by excessive body fat, and so is glucose metabolism. Obesity is associated with leptin and insulin resistance, which are precursors of diabetes type 2.

Some body fat is necessary for survival; that is normally called essential body fat. The table below (from Wikipedia) shows various levels of body fat, including essential levels. Also shown are body fat levels found in athletes, as well as fit, “not so fit” (indicated as "Acceptable"), and obese individuals. Women normally have higher healthy levels of body fat than men.

If one is obese, losing body fat becomes a very high priority for health reasons.

There are many ways in which body fat can be measured.

When one loses body fat through fasting, the number of adipocytes is not actually reduced. It is the amount of fat stored in adipocytes that is reduced.

How much body fat can a person lose in one day?

Let us consider a man, John, whose weight is 170 lbs (77 kg), and whose body fat percentage is 30 percent. John carries around 51 lbs (23 kg) of body fat. Standing up is, for John, a form of resistance exercise. So is climbing stairs.

During a 24-hour fast, John’s basal metabolic rate is estimated at about 2,550 kcal/day. This is the number of calories John would spend doing nothing the whole day. It can vary a lot for different individuals; here it is calculated as 15 times John’s weight in lbs.

The 2,550 kcal/day is likely an overestimation for John, because the body adjusts its metabolic rate downwards during a fast, leading to fewer calories being burned.

Typically women have lower basal metabolic rates than men of equal weight.

For the sake of discussion, we expect each gram of John’s body fat to contribute about 8 kcals of energy, assuming a rate of conversion of body fat to calories of about 90 percent.

Thus during a 24-hour fast John burns about 318 g of fat, or about 0.7 lbs. In reality, the actual amount may be lower (e.g., 0.35 lbs), because of the body's own down-regulation of its basal metabolic rate during a fast. This down-regulation varies widely across different individuals, and is generally small.

Many people think that this is not much for the effort. The reality is that body fat loss is a long term game, and cannot be achieved through fasting alone; this is a discussion for another post.

It is worth noting that intermittent fasting (e.g., one 24-hour fast per week) has many other health benefits, even if no overall calorie restriction occurs. That is, intermittent fasting is associated with health benefits even if one fasts every other day, and eats twice one's normal intake on the non-fasting days.

Some of the calories being burned during John's 24-hour fast will be from glucose, mostly from John’s glycogen reserves in the liver if he is at rest. Muscle glycogen stores, which store more glucose substrate (i.e., material for production of glucose) than liver glycogen, are mobilized primarily through anaerobic exercise.

Very few muscle-derived calories end up being used through the protein and glycogen breakdown pathways in a 24-hour fast. John’s liver glycogen reserves, plus the body’s own self-regulation, will largely spare muscle tissue.

The idea that one has to eat every few hours to avoid losing muscle tissue is complete nonsense. Muscle buildup and loss happen all the time through amino acid turnover.

Net muscle gain occurs when the balance is tipped in favor of buildup, to which resistance exercise and the right hormonal balance (including elevated levels of insulin) contribute.

One of the best ways to lose muscle tissue is lack of use. If John's arm were immobilized in a cast, he would lose muscle tissue in that arm even if he ate every 30 minutes.

Longer fasts (e.g., lasting multiple days, with only water being consumed) will invariably lead to some (possibly significant) muscle breakdown, as muscle is the main store of glucose-generating substrate in the human body.

In a 24-hour fast (a relatively short fast), the body will adjust its metabolism so that most of its energy needs are met by fat and related byproducts. This includes ketones, which are produced by the liver based on dietary and body fat.

How come some people can easily lose 2 or 3 pounds of weight in one day?

Well, it is not body fat that is being lost, or muscle. It is water, which may account for as much as 75 percent of one’s body weight.


Elliott, W.H., & Elliott, D.C. (2009). Biochemistry and molecular biology. New York: NY: Oxford University Press.

Fleck, S.J., & Kraemer, W.J. (2004). Designing resistance training programs. Champaign, IL: Human Kinetics.

Large, V., Peroni, O., Letexier, D., Ray, H., & Beylot, M. (2004). Metabolism of lipids in human white adipocyte. Diabetes & Metabolism, 30(4), 294-309.

Tuesday, February 16, 2010

Large LDL and small HDL particles: The best combination

This post has been revised and re-published. The original comments are preserved below.

Tuesday, February 9, 2010

Lucy was a vegetarian and sapiens an omnivore: Plant foods as natural supplements

Early hominid ancestors like the Australopithecines (e.g., Lucy) were likely strict vegetarians. Meat consumption seems to have occurred at least occasionally among Homo habilis, with more widespread consumption among Homo erectus, and Homo sapiens (i.e., us).

The figure below (from:; click on it to enlarge) shows a depiction of the human lineage, according to a widely accepted theory developed by Ian Tattersall. As you can see, Neanderthals are on a different branch, and are not believed to have been part of the human lineage.

Does the clear move toward increased meat consumption mean that a meat-only diet is optimal for you?

The answer is “perhaps”; especially if your ancestors were Inuit and you retained their genetic adaptations.

Food specialization tends to increase the chances of extinction of a species, because changes in the environment may lead to the elimination of a single food source, or a limited set of food sources. On a scale from highly specialized to omnivorous, evolution should generally favor adaptations toward the omnivorous end of the scale.

Meat, which naturally comes together with fat, has the advantage of being an energy-dense food. Given this advantage, it is possible that the human species evolved to be exclusively meat eaters, with consumption of plant foods being mostly optional. But this goes somewhat against what we know about evolution.

Consumption of plant matter AND meat – that is, being an omnivore – leads to certain digestive tract adaptations, which would not be present if they were not absolutely necessary. Those adaptations are too costly to be retained without a good reason.

The digestive tract of pure carnivores is usually shorter than that of omnivores. Growing a longer digestive tract and keeping it healthy during a lifetime is a costly proposition.

Let us assume that an ancient human group migrated to a geographical area that forced them to adhere to a particular type of diet, like the ancient Inuit. They would probably have evolved adaptations to that diet. This evolution would not have taken millions of years to occur; it might have taken place in as little as 396 years, if not less.

In spite of divergent adaptations that might have occurred relatively recently (i.e., in the last 100,000 years, after the emergence of our species), among the Inuit for instance, we likely have also species-wide adaptations that make an omnivorous diet generally optimal for most of us.

Meat appears to have many health-promoting and a few unhealthy properties. Plant foods have many health-promoting properties, and thus may act like “natural supplements” to a largely meat-based diet. As Biesalski (2002) put it as part of a discussion of meat and cancer:

“… meat consists of a few, not clearly defined cancer-promoting and a lot of cancer-protecting factors. The latter can be optimized by a diet containing fruit and vegetables, which contain hundreds of more or less proven bioactive constituents, many of them showing antioxidative and anticarcinogenic effects in vitro.”


Biesalski, H.K. (2002). Meat and cancer: Meat as a component of a healthy diet. European Journal of Clinical Nutrition, 56(1), S2-S11.

Thursday, February 4, 2010

How much vitamin D? Vitamin D Council's recommendations

Since my recent post on problems related to vitamin D deficiency and excess I received several questions. I have also participated in several discussions in other blogs related to vitamin D in the past few days.

There is a lot of consensus about vitamin D deficiency being a problem, but not much about vitamin D in excess being a problem as well.

Some bloggers recommend a lot of supplementation, which may be dangerous because: (a) our body evolved to obtain most of its vitamin D from a combination of sunlight exposure and cholesterol, and thus body accumulation regulation mechanisms are not designed to deal with excessive oral supplementation; and (b) vitamin D, like many fat-soluble vitamins, accumulates in fat tissue over time, and is not easily eliminated by the body when in excess.

The Vitamin D Council has the following general recommendation regarding supplementation:
Take an average of 5,000 IU a day, year-round, if you have some sun exposure. If you have little, or no, sun exposure you will need to take at least 5,000 IU per day. How much more depends on your latitude of residence, skin pigmentation, and body weight. Generally speaking, the further you live away from the equator, the darker your skin, and/or the more you weigh, the more you will have to take to maintain healthy blood levels.
They also provide a specific example:
For example, Dr. Cannell lives at latitude 32 degrees, weighs 220 pounds, and has fair skin. In the late fall and winter he takes 5,000 IU per day. In the early fall and spring he takes 2,000 IU per day. In the summer he regularly sunbathes for a few minutes most days and thus takes no vitamin D on those days in the summer.
For those who have problems with supplementation, here is what Dr. Cannell, President of the Vitamin D Council, has to say:
For people who have trouble with supplements, I recommend sunbathing during the warmer months and sun tanning parlors in the colder months. Yes, sun tanning parlors make vitamin D, the most is made by the older type beds. Another possibility is a Sperti vitamin D lamp.
One thing to bear in mind is that if your diet is rich in refined carbohydrates and sugars, you need to change that before you are able to properly manage your vitamin D levels. You need to remove refined carbohydrates and sugars from your diet. No more white bread, bagels, doughnuts, table sugar, sodas sweetened with high-fructose corn syrup; just to name a few of the main culprits.

In fact, a diet rich in refined carbohydrates and sugars, in and of itself, may be one of the reasons of a person''s vitamin D deficiency in the case of appropriate sunlight exposure or dietary intake, and even of excessive levels of vitamin D accumulating in the body in the case of heavy supplementation.

The hormonal responses induced by a diet  rich in  refined carbohydrates and sugars promote fat deposition and, at the same time, prevent fat degradation. That is, you tend to put on body fat easily, and you tend to have trouble burning that fat.

This causes a "hoarding" effect which leads to an increase in vitamin D stored in the body, and at the same time reduces the levels of vitamin D in circulation. This is because vitamin D is stored in body fat tissue, and has a long half-life, which means that it accumulates (as in a battery) and then slowly gets released into the bloodstream for use, as body fat is used as a source of energy.

It should not be a big surprise that vitamin D deficiency problems correlate strongly with problems associated with heavy consumption of refined carbohydrates and sugars. Both lead to symptoms that are eerily similar; several of which are the symptoms of the metabolic syndrome.