Burn It Up
Learn how to rev up your metabolism and keep off extra weight

By Catherine Monahan

Cold-weather months signal nature's most austere time of year, though the sparseness doesn't stop many of us from indulging in more food and less exercise. Winter celebrations often include an unfortunate tradition of post-holiday weight gain. But there's hope: This seasonal pattern springs more from bad habits than from deep-down biological cues. Losing the extra weight is basic. It comes down to understanding metabolism, your body's natural weight-loss aid.

Metabolism is energy management. It's the thousands of chemical reactions within a cell that turn food into fuel. Picking up where digestion leaves off, metabolism converts complex nutrient molecules into simpler forms and frees valuable energy in the process. The power released by breaking down sugar glucose into water and carbon dioxide contracts muscle cells, moves chromosomes and pumps chemicals across cell membranes.

Calories are the currency of metabolism, and how quickly cells convert food into these units of energy is called the metabolic rate. The metabolic rate is influenced, in part, by the number of calories you burn while resting to power such tasks as breathing, heartbeat and brain activity. This basal metabolic rate (BMR) can account for more than half of the calories you burn each day. How you burn the other half is largely up to you.

How Fast Can You Go?
Your metabolic rate is regulated by thyroid hormones that signal cells to work harder and organs to run faster according to the body's energy needs. How cells respond is somewhat inheritable. So-called thrifty genes enable certain people to readily convert excess calories to fat, whereas a quite different gene appears instead to turn extra food energy into heat. Which gene type you inherit may dictate your metabolic speed.

Genetics also determines your body shape and the percent of muscle or fat it carries. If your body bears more muscle, you likely have a high metabolism. Energy-hungry muscle cells burn more calories than fat cells do, even while you're sleeping. It's the reason why men, who have more lean muscle than women, tend to lose weight quickly and gain it back slowly. Older people often put on pounds as their metabolisms slow, but the reason has more to do with shrinking muscle mass than with age. Starting at age 30, a sedentary person can expect to lose 10 percent of her muscle mass each decade of life thereafter. When muscle shrinks, metabolism slows and fat moves in to make up the difference.

Weight-loss aids that claim to speed metabolism have nothing to do with genes or lean muscle. Instead, they often contain ephedrine, a central nervous-system stimulant derived from the ephedra plant (Ephedra sinica) that speeds up basic body functions—sometimes dangerously so among people with certain health conditions. The problem with relying on such products, says Stephen Wangen, ND, is that they're a temporary metabolic fix. "If you don't take them, your rate will go back down," he says. Your best bet is to work with what you've got.

Speed It And Feed It
Weight training is the most effective, lasting route to increasing lean muscle mass and speeding your metabolism. In the same way that aerobic exercise forces heart muscle to adapt to increased cardiovascular demands, weight lifting forces leg, arm and back muscles to grow and strengthen. Larger muscles demand more energy, and metabolism shifts into high gear to supply it.

Exercising for just 20 to 30 minutes is enough to increase metabolic rate and boost calorie burning for several hours, says Wangen. "Of course, the more you exercise, the more you raise the metabolic rate—not just for hours, but for days and months," he says.

Once you've upped your metabolism, you must feed it. And that's where many of us go awry, says Derek Johnson, a Los Angeles dietitian. "Most people don't eat enough calories," he says. "They view foods as so adversarial that they cut back."

Eating too little almost always backfires. Once you stop eating, the body perceives starvation and slows its metabolic rate. "Our bodies were designed to operate in a much different environment, and survival depended on conserving energy," explains Wangen. Inconsistent eating can have the same effect. It takes the average person 48 hours to maximize metabolism, says Johnson, and one missed meal can negate several days of healthy eating.

"The biggest rule is to not go more than three hours without eating," he says. "You don't want to let your blood sugar drop." Johnson recommends having small meals throughout the day, including snacks between breakfast and lunch.

The foods you choose can also make or break your metabolic rate. Fats, protein and complex carbohydrates take longer to digest and have more staying power than the simple sugars found in sweets. Imagine the body as a furnace, foods as fuel, and metabolism as a heat pattern, says Johnson. "If you're feeding your body with newspaper, you're going to get a quick energy burst and then a quick drop," he explains. "We want to choose foods that are more like coal, that create a very hot heat pattern."

Match Your Metabolism
You are unique and so is your metabolism. It's the reason, says Johnson, that a high-carbohydrate diet may work wonders for one person and send another into a sleepy stupor. Choosing foods that suit your metabolism is a more precise way to increase energy and prompt weight loss.

According to Johnson, there are three basic metabolic types (see "What's Your Type?"). Blood tests can determine your category, says Johnson, but in lieu of lab work, go by how you feel. For instance, a tendency to be groggy in the early morning or afternoon is a good sign that you need more fat in your diet.

Drinking plenty of purified water will speed up any metabolism—three-fourths ounce per pound of body weight daily, or about 11 glasses a day for an average person. "If you're not drinking water, but you're still eating decently and going to the gym, you will not metabolize fat at the rate you need to," says Johnson. When the body perceives thirst, metabolism slows, just as it does if you skip a meal. "If people just increased their water intake and added snacks between meals, regardless of their type of metabolism, they would lose weight and feel much better," he says.

Sound simple? It is. Exercise your body, feed it well, and it will pay you back with lifelong health.

Catherine Monahan is a health and science writer and a frequent contributor to Delicious Living.