The soybean is the great impostor. When used as a substitute for meat, which it does well because of its protein profile, a serving of soybeans can save you fat, especially saturated fat. You also get a fantastic fiber boost, both soluble and insoluble.
Though the United States is the world's largest grower of soybeans, more than half of the crop is exported. Soybeans are one of the best plant sources of protein, nearly mimicking the perfect protein profile of milk.
For fighting fat, you just can't beat soybeans for their versatility. Though surprisingly high in fat for a bean, it's mostly the healthy unsaturated kind. By lowering your blood level of LDL cholesterol (the "bad" cholesterol), soybeans' unsaturated fat is thought to reduce the risk of heart disease. Soybeans also happen to be one of the few plant sources of omega-3 fatty acids, which may aid in the battle against heart disease and cancer as well as arthritis.
Soybeans are loaded with a phytochemical called isoflavone, which may help combat breast tumors by dampening the ill effects of estrogen-like compounds. This fact may partly explain why Asian women, whose diets are typically rich in soybeans, are less likely to develop breast cancer than American women (soybeans are often poorly represented in American diets).
Isoflavones in soy products (not in isolate supplements) appear to help reduce cholesterol levels and offer other protection for your heart. One of the isoflavones in soybeans, called genistein, may affect the body's fat cells, reducing production of them and making them smaller. It showed promise in studies done in mice. Genistein's possible ability to help you stay lean is being studied further.
Most soy products contribute some calcium; tofu with calcium sulfate or calcium chloride is an even better source of the bone-building mineral.