Most endurance athletes are concerned about their weight and periodically diet. Since each pound contains about 3,500 calories, if we reduce caloric intake by 1,000 calories a day, we lose about two pounds each week. Logically, the higher the daily caloric deficit, the faster the weight loss. But not all weight loss is good weight loss, and unfortunately, the faster you drop weight, the more muscle you lose.
This observation was made by researchers at Rockefeller University. Researchers looked at the effect of different daily caloric deficits on weight loss. As might be expected, the fewer calories the subjects consumed, the more weight they lost. What wasn’t expected was where the weight loss came from. In individuals who moderately reduced their daily caloric intake, 91% of the loss was fat and only 9% was muscle. But in subjects who severely reduced their daily caloric intake, fat represented 48% of the total weight loss and muscle 42%. In other words, the greater the daily calorie restriction, the greater the loss of muscle mass. For endurance athletes, loss of muscle mass can produce a decrease in strength, power and a decline in overall performance..
This research also explained why the longer one is on a diet that severely restricts calories, the harder it is to keep losing weight. As the body loses more muscle mass, the body’s overall metabolic rate decreases, since a resting muscle cell burns almost eight times more energy per day than a fat cell.
Ironically, severe calorie restrictions are unnecessary. A recent study showed that a group that maintained a 200-calorie-per-day deficit lost as much weight in six months as a group that maintained a 750-calorie-per-day deficit. The bottom line: if you want to lose fat, not muscle, a moderate diet plan is the only way to go.
Dr. Robert Portman, a well-known sports science researcher, is coauthor of Nutrient Timing and Hardwired for Fitness and the creator of The Portman Calculator: the first-ever online calculator for hydration & fitness.