SCIENCE: How Weight Training May Help With Weight Control: People who regularly do muscle-strengthening exercises are about 20 to 30 percent less likely to become obese over time than people who do not. “The benefits remained when the researchers controlled for age, sex, smoking, general health and aerobic exercise. People who worked out aerobically and lifted weights were much less likely to become obese. But so were those who lifted almost exclusively and reported little, if any, aerobic exercise.”

Plus, a reminder: “B.M.I. does not differentiate muscle from fat, Dr. Brellenthin points out. If you add muscle with weight training, your B.M.I. can rise.”