A study in the April 1999 issue of the Journal of the American College of Nutrition proved the calorie-burning benefits of muscle. The study put two groups of obese individuals on a very low-calorie diet. One group did only aerobic exercises four times per week while the other group did only resistance exercises three times per week. After 12 weeks, the aerobics group lost more weight than the resistance group. However, in the aerobics group almost one third of the weight lost was muscle. The resistance group lost only fat.
At its core, burning fat comes down to the process of lipolysis—the breaking down of fat lipids, explains Seedman. This happens in the mitochondria of the muscles, or the powerhouses of the cells, responsible for generating the energy our cells need to do their jobs. Exercise has been shown to improve mitochondria function, which then promotes fat breakdown, Seedman adds. Plus, working out helps regulate pretty much all the hormones that optimize fat loss.