Short - term studies have shown that endurance exercise without caloric restriction causes weight less- However,
exercise by itself is less effective than caloric restriction (i.e. , dieting) or caloric restriction plus exercise. Studies have shown that exercise plus diet is more effective than dieting alone in maintaining weight loss (six months to three years after the beginning of the program).
Dieting by itself reduces lean body mass and decreases resting metabolic rate, sometimes by as much as 30% . During the initial stages of a starvation diet, 40% of the weight loss may be from lean mass. Most studies have shown that after one year, most weight lost through dieting alone is regained, and the dieter may become involved in a futile cycle of dieting and regained weight.
To be successful, long - term weight - control programs should include exercise. Exercise spares lean mass and increases resting metabolic rate during caloric restriction. Exercise also increases the thermic response to food (i.e. , digesting and processing food increases metabolic rate) . In addition, exercise exerts an independent effect on reducing the risk of coronary artery disease.
Exercise intensity may be important for increasing metabolic rate. Several studies have shown that intense exercise increases metabolic rate in obese subjects, while moderate exercise does not. Ute metabolic effects of exercise are temporary, however. In dieters, metabolic rate decreases when training is suspended for as little as three days.
The literature is unclear on the effects of exercise on food intake. Studies have found decreased, increased, and no change in food intake in people involved in moderate exercise. Likewise, it is not known if exercise influences dietary composition (i.e., the percentage of fats and carbohydrates in the diet).
Weight training has been suggested as an important component in a long - term weight - management program . Programs stressing caloric restriction cause decreases in lean body mass, negative nitrogen balance (i.e. , body loses protein) , and diminished muscle strength. Including weight training in the weight - reduction program helps spare lean body mass and maintain nitrogen balance. Also, improvements in strength between 17% and 22% have been reported in subjects who weight - trained during caloric restriction. Lean mass is the most important determinant of resting metabolic rate. Weight training increases or maintains lean mass in people on low -calorie diets.
Like endurance exercise, weight training has no effect on regional fat deposition (i.e., spot reducing is ineffective) . Although the improved muscle tone that results from training usually makes a particular area of the body look better, the subcutaneous adipose layer that lies over the muscles is unaffected .
