What Affects Your Metabolism
I'm living proof that you can't judge a metabolism by its cover. You and I could be the same height and weight, have the same BMI, and even fit into the same J Brand jeans, but have wildly different flab-to-muscle proportions, making one of us the calorie-burning equivalent of a Bic lighter and the other of a blowtorch.
Metabolism, simply put, is the total number of calories your body burns each day. Sixty-five percent of those calories are used up for 24-7 functions like breathing and circulation -- the top burners are your brain, liver, heart, and kidneys -- with another 10 percent devoted to the process of digesting the very foods that may have given you that muffin top in the first place. The remaining 25 percent of the calories you burn can be chalked up to the physical activity you do in a day -- not just Spinning class but every move you make, including standing in line or tweeting your latest DEXA scan results.
You've heard it before: The more muscle you have, the more calories you burn. In fact, lean tissues, including organs and muscles, on average burn 14 calories a pound a day, while fat only burns about three calories per pound, Dr. Heber says.
Simply put, whether you're Kate Moss or Kirstie Alley, it's the absolute amount of muscle in you that determines the overall speed of your resting metabolism -- the amount you burn just sitting around -- and some of us are born with an edge in the amount of muscle fibers we've got. But don't blame bad genes for your extra flab. "It's your environment -- that is, food and activity -- that is extremely important in ultimately determining your weight," says Andrew G. Swick, PhD, director of obesity and eating disorders research at the University of North Carolina at Chapel Hill Nutrition Research Institute in Kannapolis.
And there's plenty you can do to not only add muscle but also maximize your metabolism along the way.
Keep your heart pumping for fast results
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.
Don't let your body run a empty fumes.
What to Eat for a Faster Metabolism
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."
