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Written by By Dan Gwartney, MD
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Tuesday, 13 January 2009 |
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Page 2 of 4
Yet, there is a silver lining to the large-scale social experiment that was the Atkins craze. It stimulated research in the field of fat loss and pressured the editors of medical and science journals to publish articles that otherwise would have been passed over, since weight loss is considered to be a trivial subject by many professionals. A great deal has since been learned about fat loss. Given the success of low-carbohydrate dieting and the focus placed on the hormone insulin, which controls blood sugar, many researchers designed and reported on elaborate studies that investigated insulin’s role in weight management with unprecedented detail.
Though often thought of in terms of its role in regulating blood sugar and treating diabetes, insulin has other functions. Among these is the regulation of fat stores in adipocytes (fat cells). Fat cells are sensitive to a number of hormones that control whether fat is taken up from the bloodstream and stored or if stored fat is broken down and released back into the circulation; chief among these hormones is insulin.
 Insulin carries a double-whammy of obesity, in that it is able to increase fat storage as well as reduce fat loss. This comment has been repeated time and again. Knowing what insulin does (increase fat storage and decrease fat loss), it then becomes useful to understand how that happens if one is interested in fat loss or weight management. Fortunately, an excellent series of experiments were recently published in the Kobe Journal of Medical Sciences revealing how insulin prevents fat loss. How insulin increases fat storage will not be addressed in this article.
In the fat cell, fat is stored in large globules surrounded by a thin protein-based envelope called perilipin. Think of perilipin as a Ziploc bag. The stored fat is present in a form called a triglyceride, which is three fatty acids, each attached to a common glycerol molecule. It is like a three-legged stool, with glycerol being the seat and each fatty acid being one of the three legs. In order for the fat to be released into the bloodstream, the perilipin envelope has to open so that an enzyme can attach to the triglycerides and break it down to fatty acids and glycerol.
There are a number of hormones and neurotransmitters that stimulate fat loss. People are most familiar with adrenalin, also called epinephrine, and the related neurotransmitter norepinephrine. Adrenalin stimulates fat loss by activating a class of receptors called beta-adrenergic receptors that are present on the surface of a fat cell. In humans, specific types of beta-adrenergic receptors account for the vast majority of the fat loss signal, those being the beta1- and beta2-adrenergic receptors (abbreviated by the Greek symbol ß1 and ß2). ß receptors can be stimulated by a number of drugs; ephedrine-caffeine supplements worked well for fat loss by increasing ß stimulation.
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Research and Review 
