Diet and Exercise

Even though you can lose weight by diet or exercise, for reasons explained below, we recommend that you use a combination of the two to achieve your goal.

When you reduce your caloric intake, your body responds as if you are beginning to starve. One of the body's adaptations is to decrease the resting metabolic rate to save the body's energy stores. This means that a diet very low in calories can become counterproductive to weight loss; the more you cut back on caloric intake, the more the body responds by decreasing its energy expenditure.

When you lose weight by diet alone, 35 to 45 percent of the weight lost is lean tissue, not fat tissue. Therefore, you could actually lose weight but not change your percent of body fatness (body composition) very much. This loss of lean tissue also contributes to the body's reduction in resting metabolic rate, making it more difficult for you to lose weight. Resistance training can increase muscle mass and help maintain the resting metabolic rate.

A weight-loss program that uses diet alone results in a slower rate of fat loss. It should be no surprise, then, that a combination of diet and exercise is recommended to achieve weight-loss and body-composition goals. Exercise helps to maintain lean muscle tissue and the resting metabolic rate while more fat is being lost; the body actually makes changes in percent body fat faster than it can through diet alone. We have seen many cases in which body weight may not change for several weeks but clothing sizes do. Why does this happen? The exercise is increasing lean body mass while fat mass is decreasing slightly. With time, body weight will decrease in proportion to the change in energy balance.