Myth: You can burn fat by eating certain foods, like grapefruit and cabbage soup.

Fact: The grapefruit diet requires you to eat half a grapefruit before every meal to reap the benefits of the fruit's so-called fat-burning enzymes. Calories typically are limited to fewer than 800 a day, although some versions require that you eat until you are full. Grapefruit has no fat, is low in calories and sodium, and is packed with vitamin C. But the very low calories — and deficits in protein, fiber and several important vitamins and minerals — can make this diet dangerous. Similarly, the cabbage soup diet proponents report feeling lightheaded and weak because the diet is too low in protein, vitamins and complex carbohydrates. You may lose weight, but you'll probably be too queasy to enjoy it. Remember, no foods can burn fat. Caffeine-rich foods may speed up your metabolism rate for a short time. However, they do not cause any weight loss. The best way to lose weight is to reduce the number of calories you eat and increase your physical activities.