"Exercise is fun,” says James Moriarity, M.D., president of the American Medical Society for Sports Medicine. “It’s a great way to interact socially, and it has tremendous health benefits.” Need even more motivation? Work out with a friend — you’ll be less likely to bail. Unless you have a chronic health condition (like diabetes or heart disease), you can walk, bike, or use an elliptical cross-trainer without consulting a doctor.

To stay committed, don’t overreach. Start slowly, and work up to 30 to 45 minutes most days of the week. “If you can speak conversationally, you’re working at the right intensity,” says Cedric Bryant, Ph.D., chief exercise physiologist for the American Council on Exercise. Be sure to warm up and cool down for 5 to 10 minutes, and include strength training twice a week. Try Pilates, yoga, or resistance exercises (download illustrated guides at www.acefitness.org). If you experience extreme pain (especially in a joint), dizziness, or labored breathing, see a doctor.