“The beauty of your metabolism is that it can be manipulated,” writes self-proclaimed “metabolism whisperer” Haylie Pomroy in her book The Fast Metabolism Diet, which claims to “set your metabolism on fire.”

“When we talk about metabolism, we’re talking about the calories you burn when you’re not doing anything, or your resting metabolism,” says Michael Jensen, director of the Obesity Specialty Council at the Mayo Clinic.

“Unfortunately, we don’t have much control over our resting metabolism.”

Metabolism slows as you age

“If you compare a 70-year-old and a 20-year-old with the same amount of fat and lean tissue, the 70-year-old would burn fewer calories at rest than the 20-year-old,” says Jensen.

Women also have a slower metabolism than men, largely because they typically have less muscle. (You have to burn more calories to maintain muscle than fat.)

Even if men didn’t have more muscle, says Jensen, “for any given amount of fat and lean tissue, women burn slightly fewer calories at rest than men.”

Can anything boost your resting metabolism?

“People who gain a lot of extra muscle will burn more calories at rest than before they gained all that muscle,” says Jensen.

But the effect isn’t huge.

“For the average person, muscle accounts for about 25 percent of metabolic rate,” notes Jensen. “So you’d have to gain a lot of muscle before it would have much impact on your resting metabolism.”

Want a bigger calorie burning boost? Spend less time at rest.

“You’ll burn more calories from doing that strength training than you’ll burn from the increased muscle mass,” says Jensen. Or walk, run, bike, or do other aerobic exercise to burn more calories.

If your resting metabolism is slow, don’t despair

Jensen’s team tracked people with either high or low metabolic rates. Those in the “high” group burned about 500 calories more per day than those in the “low” group, despite being roughly the same age and having similar amounts of fat and muscle mass. Yet after roughly ten years, weight gain was no different.

“A low metabolic rate doesn’t mean you’re doomed to gain weight,” says Jensen, “and a high metabolic rate doesn’t protect you from gaining weight.”

The bottom line

Ignore the hype about resetting or revving your resting metabolism. Instead, get moving.