Clients -- and just about everyone I meet who learns I'm a nutritionist -- ask me this question all the time: How can I boost my metabolism?

Metabolism is simply the total of all body processes that burn calories -- your basal metabolic rate plus your activity factor. When it comes to improving your metabolism, there's good news and bad news.

First the bad news: Most of what controls your metabolism isn't under your control. Some people are genetically blessed with a high-burning metabolism. They didn't ask for it, they were born with it. (So don't hate them for it, unless, of course, they rub it in!) On average, men have a metabolism that is 10 to 15 percent higher than women's, mainly because of their larger size and greater muscle mass. Whether you're a man or a woman, your metabolism naturally decreases with age. Scientists have estimated that metabolism slows about 5 percent per decade, beginning at age 40, as we lose muscle mass and increase body fat. Hypothyroidism (under-active thyroid) lowers metabolism and causes weight gain. Fortunately in this case, if a blood test confirms there's a problem, your doctor will prescribe medication that can boost it back up to baseline.

Now the good news: Your metabolism doesn't have to remain stagnant or take a nosedive. You can burn more calories, lose more weight, just by changing the way you think about eating and moving.

Food Fixes for Metabolism
Remember -- our basal metabolic rate includes the energy we need for body processes, including digestion. About 10 percent of our calories are used to process the food we eat. As the calories are burned, our bodies generate heat. This phenomenon, known as the thermic effect of food, is influenced by how much, how often, and what we eat. In addition, food can directly affect metabolism by altering the way the body functions (which changes the amount of energy it needs). Here are my best recommendations for maximizing metabolism:

• Eat at least 1,000 calories per day. Although it is generally true that eating a low-calorie diet will help you take off weight, if you eat too few calories, your metabolism will get slower and slower as it tries to conserve energy. As your metabolism crashes, the weight you take off will most likely creep back on over time. Plus, you'll be more likely to binge on junk food if you reduce your calories by too much.
• Eat every four to five hours. A regular meal schedule helps keep your body working to digest and absorb foods. Between breakfast and bed, aim to eat a meal or snack every four to five hours. And try to eat breakfast within 90 minutes of rising. People who regularly eat a 
  healthy breakfast are more likely to control their weight. If you wait to eat until you're really ravenous, you're more likely to overeat later in the day. Also breakfast helps fire up your metabolism after a full night on a slow simmer.
• Eat protein with every meal. All foods contribute to the thermic effect, which means that all foods -- carbohydrates, fats, and proteins -- help to give metabolism a gentle nudge higher when we eat them. But protein has the greatest thermic effect of all. In addition, protein can increase metabolism by helping to maintain and build muscle mass.

Exercise Fixes for Metabolism
A big percentage of your maintenance calories -- the amount you burn in the course of a clay -- comes from your activity level. If you go from having average activity levels to being extremely active, you can double the amount of calories burned (that's activity factor calories, not BMR calories). This is why any activity -- every extra step you take -- can help boost your metabolism. Part of my recommendation is to move as much as possible: climb the stairs instead of taking the escalator, park at the opposite end of the mall and walk to your favorite store, garden instead of watching TV . . . anything, as long as it is movement.

In addition, I strongly encourage everyone to exercise regularly. The optimal weight-loss exercise program consists of both aerobic exercise and strength training. Regular exercise can increase your activity factor and your metabolism. As you get older and your metabolism slows, you can rebalance your energy needs by increasing the duration or intensity of your workouts.

• Aerobic exercise. Aerobic exercises use energy and increase many different metabolic processes (such as your heart rate), all of which burn calories. All aerobic activities -- including running, brisk walking, swimming, skating, skiing, and cycling -- increase metabolism while you're exercising, and also keep your metabolism burning higher for hours afterward. I recommend doing some form of aerobic activity four or five days per week, for at least 30 minutes per day.
• Strength training. Exercises that work your muscles without necessarily raising heart rate are considered strength training. These include lifting weights, working with resistance bands, yoga, Pilates, circuit training, and calisthenics (including push-ups, chin-ups, and abdominal crunches). These activities directly increase your BMR by building muscle, so you will burn more calories every minute of every day. I recommend doing some form of strength training two or three days per week. Plan a strength training regimen that's realistic for both your schedule and personality. For some people that may mean 15 minutes of calisthenics in the privacy of your bedroom, and for others it may involve a more elaborate weight-training regimen at the gym.

Reprinted from: Joy Bauer's Food Cures: Treat Common Health Concerns, Look Younger & Live Longer by Joy Bauer, MS, RD, CDN with Carol Svec. Copyright © 2007 Joy Bauer, MS, RD, CDN. (Published by Rodale; April 2007;$18.95US/$22.95CAN; 978-1-59486-466-7) Permission granted by Rodale, Inc., Emmaus, PA 18098. Available wherever books are sold or directly from the publisher by calling at (800) 848-4735.

Author
Joy Bauer, MS, RD, CDN, is the nutrition expert for the Today show and Yahoo.com, and monthly weight-loss columnist for SELF magazine. She has built one of the largest nutrition centers in the country, with offices in Manhattan and Westchester County, New York. Her clientele includes high-profile professionals, celebrities, Olympic gold medalists, and the New York City Ballet. The author of several best-selling books, she lives in New York.

For more information, please visit www.joybauernutrition.com.