In a study funded by a whey protein manufacturer, clinically obese people who used whey protein as part of a calorie-reduction program lost about the same amount of weight as people who cut out the same number of calories but didn't use whey protein. The difference was in the kind of weight they lost. The people who used whey protein lost body fat, not muscle [source: Frestedt].
Being able to lose weight but hang onto lean muscle has some important health implications. For one thing, your base metabolism is higher if you have a higher muscle-to-fat ratio. Your bone density may be better (low bone density is often a problem for women who have lost weight by dieting). Your hormone levels may shift, improving your body's ability to regulate its own weight. Research with rats indicates that a whey protein diet may help reduce insulin resistance, a condition -- often a precursor to diabetes -- in which normal levels of insulin are no longer adequate for metabolism [source: Belobradjic].
Of course, rats aren't the same as people, and one study is not the same thing as a law of nature. There are almost as many ideas about weight-loss regimens as there are nutritionists. Proponents of whey protein tend to fall into the camp of high-protein, low-carb weight-loss plans, such as Atkins and the South Beach Diet. Opponents of whey protein tend to be the folks who tout whole foods and vegetarianism.
Isn't it possible that, if you're taking whey protein to build muscle, it might actually lead to weight gain rather than weight loss? Fair question. And the answer is yes, it's completely possible. Whey protein is a component of many weight-gain regimens.
If you don't reduce your calories but add whey protein to the mix, you probably will gain weight. However, if you don't exercise, there's no way that whey protein will magically turn into muscle. The body will do what it does with every excess nutrient: make fat.
Sound dietary planning and physical activity remain the cornerstones of any weight loss program. Neither whey protein nor any other supplement is going to lose the weight for you. You still have to do the work. However, doing it with whey protein could be an option.
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