It is definitely possible to speed up your metabolism, that aspect of your body that burns calories. As you age, your metabolism slows down, chiefly because you lose around a half pound of muscle each year. "If you don't use the muscle, it atrophies," explains Pamela Peeke, M.D., professor of medicine at the University of Maryland and author of Fight Fat After Forty.

Here are 5 fat burners to help you slim down.

1. Avoid alcohol

Want to keep your favorite meals from going straight to your hips (thighs, belly)? Wash them down with water, not wine. Alcohol slows your metabolism by depressing the central nervous system. A British study found that when alcohol was added to a high-fat, high-calorie meal, less dietary fat was burned off and more was stored as body fat.

2. Rev up your workouts

Interval training -- in which you add bursts of high-intensity moves into your workout -- is a surefire metabolism booster, says Glenn Gaesser, Ph.D., director of the Kinesiology Program at the University of Virginia and author of The Spark. Researchers at Laval University in Quebec found that high-intensity interval training burns more fat than regular, consistent aerobic exercise. If you usually jog at a 10-minute-mile pace, for example, add a 30-second sprint every five minutes. Or add a one-minute incline to your treadmill workout every five minutes. "Even if you just have 10 minutes for a quick workout, you can walk at a normal pace and then add in a 30-second bout of speed-walking every three minutes," recommends Gaesser.

3. Do more dairy

Women who ate low-fat dairy products, such as nonfat yogurt and low-fat cheese, three to four times a day lost 70 percent more fat than low-dairy dieters, according to a study published in the journal Obesity Research. "Calcium serves as a switch that tells your body to burn excess fat faster," explains study author Michael Zemel, M.D., director of the Nutrition Institute at the University of Tennessee in Knoxville. Sorry, but you won't reap the same benefits from calcium-fortified O.J. Research shows that you get the best results from dairy products themselves, not fortified foods. Aim for 1,200 mg, which includes about three servings of dairy a day.

4. Take up a new sport

Are you like Old Faithful when it comes to your morning walk or evening jog? Know this: The more you do an activity, the more your body adapts to it, so you burn fewer calories. If you want to light a fire under your metabolism, consider cross-training. For example, if you normally walk, try biking instead. "Since you're not used to working all those different muscles, it's a more intense workout, which can translate into a greater metabolic after-burn because your body is working harder to recover and get oxygen to all your tissues," says Carol Espel, M.S., an exercise physiologist for Equinox Fitness Clubs in New York City.

5. Go fish

Break out the lemon wedges: Regular fish eaters tend to have lower levels of the hormone leptin -- good because high levels of leptin have been linked to low metabolism and obesity, says Louis Aronne, M.D., an obesity specialist at the New York Presbyterian Weill Cornell Medical Center. Try to consume three to four servings of a fatty fish, such as salmon, tuna or mackerel, each week.