A daily serving of soy protein may reduce belly fat, reports a study in Fertility and Sterility. Subjects (who were all about equally active) drank either a 12-ounce soy-powder shake or a placebo. After three months, daily soy sippers had lost about 1.7 percent of total abdominal fat; the second group experienced no loss. Geneistein-a type isoflavone, or plant estrogen-in soy may be involved: It's been shown to shrink fat cells in mice.