Supplements designated as "fat-burners" are among the most popular supplements sold today. They are popular with athletes and bodybuilders who want to lose excess body fat for competition. But their popularity extends to those who may not be interested in a bodybuilding competition or sports participation, but still want to shed excess body fat. The ads for such products tout often extreme benefits, with depictions of models showing six-pack abdominals and small waists devoid of any signs of fat. Indeed, the ads for the products often imply that using them alone will produce a significant loss of body fat even without exercise. But the salient question about fat-burner supplements is whether they actually work.
Fat-burner supplements contain a wide variety of active ingredients. Most are said to work by a thermogenic mechanism, which involves converting excess calories into heat rather than stored as fat. Such mechanisms do exist in the body. For example,in recent years it's become apparent that a special type of fat called brown adipose tissue or BAT is far more active in adults than previously believed. In the past, BAT was thought to exist in significant amounts in animals and human babies, but then dissipated in activity past infancy. On the other hand, many people seem to eat whatever they want with impunity as they never seem to gain body fat. This is often true despite diets that feature high-calorie junk foods that normally would pack the pounds on. At first, this natural resistance to weight gain was attributed to having a "higher metabolism." But when the thyroid activity of these weight-resistant people was checked, they showed normal thyroid gland function. Now we know that the reason why many people don't gain the weight expected by their dietary intake is due to having more active BAT activity, coupled with a tendency for constant movement, or "fidgeting." That latter effect is known scientifically as"non-shivering thermogenesis" and burns a surprising amount of calories each day. On the other hand, more recent research shows that the fat-loss activity of BAT may have been grossly overestimated, as will be discussed in an upcoming article in Applied Metabolics.
What has all this have to do with fat-burning supplements? As noted, the design of such supplements involves ingredients that some research indicates can provide thermogenic effects in a safe manner. Indeed, most people who tend to gain fat easily often show deficits in sympathetic response. The sympathetic branch of the autonomic nervous system produces two primary hormones, epinephrine, and norepinephrine, both of which are called catecholamines. These hormones interact with beta-adrenergic receptors on fat cells. When that happens, a cascade that results in fat mobilization occurs in the lipocytes or fat cells. Those who tend . . .