Do you believe you're doomed to be overweight due to a sluggish metabolism? New research indicates that what's wrong with your engine can be fixed. It is possible to improve metabolic functioning, and that means you can be healthier, feel younger and look better.

Doctors once thought all our bodies worked pretty much the same way when it comes to metabolism. Now they know that's not true. Genes, along with other biological predispositions, most likely influence metabolic function. You can inherit a poky metabolism, it seems, as easily as blue eyes.

A fast metabolism is easy to spot: These are the people who can chow down yet remain slim. Then there's your best friend, who seems to live on yogurt and rice cakes but is still a size 16. A slow internal engine, left unchecked, usually leads to weight gain and obesity.

Right now there are no safe, effective medications to speed up your metabolism and help you lose weight, says Barry Goldstein, M.D., Ph.D., chief of endocrinology at Jefferson Medical College in Philadelphia. "Lifestyle changes are the only viable alternatives for people currently struggling with metabolic problems."

That means changing what and how you eat, and increasing your level of activity. We'll show you simple, easy ways to get real results.

You Are What You Eat

Think of your metabolism as an engine fueled by food. Just as cars react differently to unleaded gas and diesel fuel, our metabolisms react to what we eat. "In terms of metabolism, the diet that works for one individual may not work for the next," says Mary Ellen Doukakis, a registered dietitian with the Clinical Nutrition Center in Denver. "Your response to protein, carbs and fat depends on your individual biochemical makeup. It's definitely an advantage to know what works for you."

Try going lighter on the carbs. Many of us may be able to boost our metabolism by replacing some carbs, including breads and starches, with protein from meat, poultry and dairy foods, according to a study published in the July 2003 issue of the American Journal of Clinical Nutrition. The participants were all overweight or obese men and women with insulin resistance. When they ate a high-protein diet—27 percent protein, 44 percent carbohydrates and 29 percent fat—the women in the study not only lost fat mass, but also kept more lean mass (muscle) during the 16-week study period. Those who didn't lose as much ate a diet consisting of 16 percent protein, 57 percent carbohydrates and 27 percent fat.

So forgo the bagel for a protein-laden scrambled egg. Replace the pasta salad with a piece of grilled chicken. Just don't cut carbs out completely, or you'll be setting yourself up for other health problems, says Dr. Goldstein. Check out, which offers meal plans and recipes from Atkins and the Zone, along with support groups, diet dia-ries and numerous other motivating resources. Cost: $5 a week.

For others, cutting back on animal protein may work better. In a 2003 nutrition study presented at a conference of the American Diabetes Association, overweight participants made their metabolisms more efficient by eating more vegetables and fruit. By gradually cutting out animal products, including meat and dairy, and keeping the use of vegetable oils very low for six months, they saw on average a 24 percent improvement in their metabolic function, says Neal Barnard, M.D., who is the author of Turn Off the Fat Genes.

Avoid traditional diet foods. Forget those lowfat foods and cottage cheese. They have a low "thermic effect," which refers to how our bodies convert calories into body heat. The goal is to burn off more calories and store less fat. Increase the thermic effect by eating high-fiber foods rich in complex carbs, not simple carbs such as sugar. Eat an apple instead of a lowfat muffin. Pass on the macaroni and cheese in favor of baked beans. By substituting 10 percent or more of your meal with high-fiber foods, you'll burn more calories for several hours, Dr. Barnard says.

How You Eat Matters

Reorienting our eating habits can also have a real impact on how efficiently our metabolism works.

Watch those portions. Some dieters don't do well eating carbs because their portions are just too big, Doukakis points out. "One-quarter cup of noodles might not be an issue to you. But if you eat one cup of noodles, your body may not respond as well. This has less to do with the carbs than it does with the portion."

Say no to crash dieting. Eating a diet of less than 1,200 calories daily often ends with an eating binge, resulting in rapid regain. Every time you do this, your body reacts by going into starvation mode, which entails water retention and, worse, a significantly slower metabolism.

But there's more reason not to crash diet. "Often when you lose and regain weight, the weight gain is in the abdominal area and leads to more central-body obesity," explains Gail D'Eramo Melkus, Ed.D., a nurse practitioner and community health educator at Yale University School of Nursing in New Haven, Connecticut. "Numerous studies have shown that central-body obesity is associated with coronary heart disease, hypertension and diabetes."

Instead, cut the portion sizes of everything you eat by one-third, suggests Melkus. In restaurants, eat smaller portions and take home the rest in a doggie bag, or share an appetizer and an entrée.

Exercise: Metabolic Magic

Calories count, of course, but activity in the form of regular exercise is key to improving how your body uses and stores what you eat.

Introduce exercise into your day. "Our research indicates that moderate exercise thirty minutes a day, along with mild weight loss aver-aging ten pounds, changes one's metabolism," Mohammed Saad, M.D., a researcher and professor of medicine at UCLA, explains. "It also reduced the development of diabetes by as much as fifty-eight percent. This is surprising."

Take a brisk half-hour walk and watch your metabolism wake up. Sit on a park bench and do leg raises. Throw in a few toe touches (or almost-touches) and waist bends. Do it several times a week and the impact on your metabolism will be profound, says Dr. Saad.

Sustain your level of activity over time. Exercise alone may help you trim down, according to a new 16-month study of young, overweight men and women at the University of Kansas. Participants were divided into two groups: One did moderate, supervised exercise, the other didn't change their activity level. Neither group dieted. Both men and women in the exercise group lost significant abdominal fat while their lean muscle mass remained the same.

Use exercise to burn off fat. Exercise triggers the body's muscles to use up calories rather than store them as fat, says Dr. Goldstein. "Maintaining muscle mass also consumes more energy for the body. In the end, exercise is the key to maintaining weight loss."

Other Factors that Can Slow You Down

How your body works is affected by more than doughnuts and sit-ups. For instance, metabolism speeds up, then slows down as we age. Take nursing mothers, for example. Breastfeeding increases their metabolism and they must eat more to keep producing enough milk for their babies. On the other hand, a woman's engine slows down during menopause because of the huge drop in hormone production. This can lead to weight gain because testosterone helps metabolize fat. So eating what used to be normal amounts actually piles on the pounds. By old age, many people slim down again and subsist on smaller amounts of food.

Poll Results: Truth Be Told

When asked why you think you gained weight, you answered:

  • Not enough exercise - 75%
  • A poor diet - 54%
  • A slow metabolism - 35%
  • I don't gain weight - 7%