Walking, skating, jogging — and eating delicious foods that fill you up — keep your metabolism chugging along at a good rate so you can take off pounds. But for maximum fat burning, here are four ways to turn up the heat.

1. Maximize your muscles. The more muscle you have, the more calories you burn even while lying poolside. But as we age, many of us lose more muscle than we gain, says Michael J. Hewitt, Ph.D., director of exercise physiology at Canyon Ranch in Tucson. The result: we burn fewer calories. The solution: strength training. Lifting weights curbs muscle loss and builds more muscle — along with a sleeker, firmer body. Two or three sessions each week (in addition to aerobic workouts) will do the trick. (For more information, see Weight Training Made Easy).

2. Vary your routine to burn more calories. “If you like cycling, walking, and swimming, do all three,” says Shawn C. Franckowiak, a consultant in exercise science at Johns Hopkins Weight Management Center in Baltimore. Different forms of exercise build and strengthen muscles in more parts of the body. Other advantages: “You’re less likely to become bored with exercise,” says Franckowiak. And your chances of getting injured are lower.