Pumping Carbon: The Fate of Fat by Jerry Brainum

 

 

If you diet and exercise properly, you will lose excess body fat. But where exactly does that lost body fat go to? If you answered "Fat City," you're wrong, but you wouldn't be alone in your misunderstanding of fat metabolism. A recent article just published in the British Medical Journal queried a number of health professionals about the fate of lost body fat. These groups included medical doctors, dieticians, and personal trainers. Almost all of them responded incorrectly when asked "Where does lost body fat go?" The majority assumed that the fate of fat was to be converted into heat or energy. This is often called a thermogenic effect. Indeed, most so-called "fat burner" food supplements work by providing a minor thermogenic effect. Studies have shown that obese people are often lacking a typical normal thermogenic response, which means their body fat doesn't respond as well to the stimulation provided by thermogenic hormones, such as epinephrine and norepinephrine. Thyroid hormone is also known to boost thermogenesis or the conversion of calories into heat. The ultimate effect, however, related to thermogenesis (which is caused by the upgraded activity of uncoupling proteins in the mitochondria portion of cells) is produced by a chemical called dinitrophenol, or "DNP." This substance produces a marked thermogenic effect through its uncoupling of oxidative phosphorylation. This is just a fancy way of saying that it inhibits the production of the basic energy substance produced in the mitochondria, adenosine triphosphate (ATP).  Because the cells cannot efficiently produce ATP when DNP is present, it must rely on other sources of energy, in this case, fat. It's possible to lose a half pound of body fat each day while using DNP. But you could also easily lose your life, since it's a very toxic chemical. The usual cause of death from DNP involves out-of-control thermogenesis, where the body cooks itself from the inside. I'll have a lot more to say about DNP in a future edition of the Applied Metabolics Newsletter.

But upgraded thermogenesis still doesn't explain precisely where fat goes to when it's lost through diet or exercise. Some of the health experts queried by the authors of the British Medical Journal article thought that the fat was turned into muscle. No doubt this misconception is based on the fact that when some people lose body fat and lift weights, the muscles get larger and more defined. To the naked eye, it appears as if the fat did indeed turn into muscle. But this is a startling notion coming from allegedly educated health professionals. It's similar to the frequent observation that muscle has "turned into fat" in those who were formerly active, but were now sedentary and who didn . . .