Our bodies store energy in two types of tissue: lean muscle and fat. Lean muscle is much more "active," burning calories at a significantly higher rate than fat does. According to studies by the American Council on Exercise, one pound of lean muscle can burn 35 to 50 calories a day, whereas a pound of fat burns only two to three calories a day!
Here's an example that illustrates the relationship between body composition and metabolism: Subject A is a woman who weighs 158 pounds and has a body fat level of 33 percent. Her resting metabolic rate (RMR) is 1,571 calories daily. Subject B is a woman who also weighs 158 pounds, but has a body fat level of 48 percent. Her RMR is considerably lower, at 1,252 calories daily. At the same weight, similar height and same age, these women have very different metabolic rates due to differences in body fat.
Clearly, the more lean muscle tissue you have, the more calories you burn. This is where strength training (usually working with weights) can play a major role in weight loss and weight maintenance. Regular strength training increases lean muscle mass, which increases your body's overall, around-the-clock, at-rest calorie-burning capacity. A modest, 20-minute workout just two or three days a week is enough to make a difference in your metabolism.
