​What is the role of exercise in weight control?

A. Exercise has traditionally been a component in weight control programs.
1. Physical activity is a factor in the weight-maintenance equation, increasing the number of calories expended.
2. Exercise builds muscle tissue, whereas dieting produces a loss of both fat and muscle; exercise combined with dieting can lead to a more favorable fat-to-muscle ratio.
3. Exercise is not effective for spot reduction.
B. Research on the role of exercise in weight loss has revealed that
1. Exercise alone can produce weight loss, but the exercise must be vigorous and frequent.
2. Exercise may raise the metabolic level, producing greater calorie expenditures than the exercise itself uses.
C. Exercise can also be beneficial for those who are not overweight, helping them to maintain a lean body mass.