Rev It Up: How to Reboot Your Metabolism

Workouts and Diets for a Faster Metabolism

Metabolism slows over time, but it doesn't do a sudden nosedive as you sit watching the American Idol finale. "Metabolism drops off 2 to 4 percent every decade as we tend to lose muscle mass," Dr. Heber explains. So, if as a twentysomething you burned 2,000 calories a day, fast-forward 10 years to your mid­thirties and you could be burning as few as 1,920 calories a day. Doesn't seem like a big difference until you do the math. Just 80 extra calories a day translates into eight pounds over a year, unless you pick up the slack with exercise.

"You can maintain your total energy expenditure as you age by combining strength training and aerobic activity. You'll probably need to do more of both," says Miriam Nelson, PhD, director of the John Hancock Research Center on Physical Activity, Nutrition, and Obesity Prevention at Tufts University in Boston. Nelson's studies in the 1990s found that a twice-weekly regimen of eight to 12 resistance exercises increased women's strength by 75 percent in one year, meaning they gained more metabolism-stoking muscle fibers. Most of those gains were in the first 12 weeks.

Even better, every workout you do will give you a metabolism boost, not just during it but also afterward. One study found that a 50-minute weight routine delivered an additional afterburn of 14 calories. Between sets, add cardio bursts or shorten the rest, and that afterburn spikes -- to the tune of 25 calories following a quickie 19-minute circuit session, according to the same study.

I tested this myself by wearing a Bodybugg device on my right biceps as I followed the FITNESS "Your Best Body Ever" with trainers Justin Ghadery and Jeff Peel at 24 Hour Fitness in West Hollywood. The device's sensors track not only your movements but also things like body temperature to continuously record the number of calories burned during the day. The highest calorie-burn days occurred when I did the total-body circuits with Peel versus any other time I went to the gym.

I saw similar afterburn increases when I added speedier bursts to my steady treadmill workouts. Scientists have measured afterburn for a half-hour jog at 35 calories, as opposed to 75 calories for 20 one-minute sprints (with two-minute rests in between).

Not only that, but "high-intensity interval training is a quick way to ramp up your body's ability to use fat as a fuel," explains Jason L. Talanian, PhD, assistant physiology professor at Fitchburg State University in Massachusetts. In a study Talanian conducted, women who did interval workouts on a stationary bike, similar to Spinning, burned 36 percent more fat when they switched back to a steady ride the following week. The speed bursts sparked a 20 percent increase in the amount of mitochondria in the exerciser's muscle cells, making it easier for the women to metabolize fat for fuel rather than carbs.

To net the afterburn uptick, "push your speed for 30 seconds when you walk or run, and then return to your usual pace for 30 seconds," Peel says. Over the course of a month Peel has me increase the ratio so I get 30 seconds of slowdown time for every minute of intense exercise.

Having a lab test indicate you're made out of jelly could send a girl off on a juice-cleanse bender, but that would actually slow your metabolism. "If you're on a very low-cal regimen -- in the 400- to 800-calorie-a-day range -- metabolism falls by 15 to 20 percent," says David Nieman, PhD, professor of exercise science and director of the Human Performance Laboratory at Appalachian State University in Boone, North Carolina. Eating less than 900 calories a day also prompts your body to burn muscle tissue as well as fat, which lowers your metabolic rate even more.

Stick with the 1,200- to 1,500-calorie a day range, Nieman suggests, and you'll still slim down without taking such a big bite out of your metabolism. "What's more, about 90 percent of the weight you lose will be fat," he says, sparing more of that calorie-burning muscle.

Another metabolism no-no that women are guilty of is ditching meals, Neiman says. "If you skip meals, you put yourself on that path toward fasting, which signals the metabolism to slow way down," he explains.

Meanwhile, Dr. Heber warns me to get more protein to help preserve the lean mass that's my metabolism workhorse. He recommends the higher end for me: 100 grams of protein a day from such foods as white meats, fish, egg whites, and soy, ­starting with breakfast. "Studies show that people who eat a high-protein breakfast control their hunger longer and their weight better," says Dr. Heber, who is the author of sensible diet books, including What Color Is Your Diet? I promptly replace my cornflake habit with egg-white omelets and the occasional whey-powder-injected pancakes.

"Think of your body as a Ferrari," says trainer Ghadery when I tell him I've turned over a new leaf with protein. "You don't put cheap gas in a vehicle like that."