What if you could control your weight just by reading this article in a comfortable chair?
That’s the promise of dietary supplements and lifestyle hacks that claim to speed up your metabolism. These products and processes, it’s said, will increase your resting metabolic rate, and voilà, you can lose weight with less calorie counting and exercise.
Sounds great, doesn’t it? Unfortunately, it doesn’t work great. Despite the hype, marketing and celebrity testimonials, ramping up your metabolism is mostly a myth. It’s akin to striving to be taller or to have greener eyes.
“There is very little hope of changing your resting metabolic rate, because you’re fighting your biology,” said Eric Ravussin, director of the Nutrition Obesity Research Center at the Pennington Biomedical Research Center in Baton Rouge, La.
To understand why trying to speed up your metabolism is mostly a waste of time and money, let’s start with some physiological background.
Your resting metabolic rate (RMR) is expressed as the number of calories your body would need if you were to do nothing for the next 24 hours. (Your basal metabolic rate is a slightly different measure, though the terms often are mistakenly used interchangeably.)
A person’s RMR is calculated by measuring oxygen consumption and carbon dioxide exhalation after the subject has been seated or lying down for at least 15 minutes and hasn’t exercised in the previous 12 hours. If the sum of someone’s daily calories consumed minus calories burned is greater than that person’s RMR, weight will increase.
How do you figure out your RMR, short of enrolling in a medical study? There are several online calculators, including the one by the National Institutes of Health, that estimate your resting metabolic rate in terms of number of calories per day. But that’s only an estimate.
People of the same sex, age, height, weight and body composition can have inherently different resting metabolic rates plus or minus 10%, said Susan Roberts, director of the energy metabolism lab at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. For example, one 35-year-old woman who is 5 feet, 6 inches tall and weighs 140 pounds might have an RBR equal to about 1,500 calories a day, while other women in the same category might need only 1,350 calories (10% less) or 1,650 calories (10% more).
A significant contributor to RMR is body composition. A 140-pound person with 15% body fat will have a higher metabolic rate than a 140-pound person with 25% body fat. Plus, Roberts said, metabolism slows by 1 to 2% per decade as a person ages.
Finally, there’s the issue of genetics. Ravussin has found family membership to be a significant factor in explaining differences in resting metabolism among people of similar size and body composition.
There are ways to pump up your RMR — briefly. But there’s nothing that will create lasting results.
Supplement makers tout ingredients such as green tea, caffeine, capsaicin and selenium as metabolism boosters. Some have been shown to slightly increase the rate at which people burn calories, but not to an extent that’s going to make a significant difference over time. We’re talking about 50 calories — the equivalent of half a banana.
Similarly, while higher-intensity workouts might result in a slight post-workout afterburn (research differs on this issue), those short-term results don’t affect what your metabolism will be the following day.
You might have read that you can pump up your metabolism by getting more sleep to keep your appetite hormones in check or by lowering your stress level so that your body doesn’t produce so much cortisol, which can lead to overeating. But those hormonal levels relate to how much you feel like eating, not how many calories a day your body burns for basic functioning.
Roberts said there are two dietary tweaks that can increase metabolism because they increase the body’s energy needs for digestion: eating more fiber and protein. She advises a diet that includes 25 to 35 grams of fiber per day (the average U.S. adult consumes about half of that) and in which protein constitutes 25 to 30% of calories.
But keep in mind that the potential payoff is modest — fewer than 100 extra calories burned per day for most people.
As for exercise, increasing your muscle mass will slightly boost your resting metabolism. But this is a different — and much more difficult — undertaking than getting stronger; you can improve your performance at bench presses without necessarily adding pounds of muscle.
“To increase muscle mass, you need very heavy-duty resistance training,” Ravussin said.
A better approach: Do heavy resistance training to slow the rate that you lose muscle mass as you age. Holding onto as much muscle as you can will keep your metabolism higher.
Ironically, while we can’t speed up our metabolism, we can slow it down. People who have lost a large amount of weight often will see their RMR drop and stay at the lower rate even if they gain back the weight. Called adaptive thermogenesis, experts attribute this phenomenon to a survival mechanism the body developed during times of famine.