Doctors at Harvard Medical School are paying more attention to belly size than to body-mass index.

They say health risks begin to mount at a measurement of 31 inches for women and 37 inches for men, especially if fat is around the abdominal organs. A waist size of 35 for women and 40 for men puts them in the danger range.

Abdominal fat is a strong risk factor for heart attacks, strokes and diabetes.

If your waist size is creeping up, the doctors say you should eat less and avoid foods that are high in fat and sugar. Eat more fruits, vegetables and whole grains, which are filling but not fattening.

You also need to exercise. If you don't have time to do much, build physical activity into your daily life. Walk up the stairs and walk to the store. Do chores around the house and the yard.

Get out for a walk or a jog a few mornings a week. The doctors say you'll be sharper at work and be able to make back the time you invested in the walk.

Set up an exercise bike at home. Use it even if it's just for five or 10 minutes.