Diet and exercise are all well and good, but what if you could also 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 voila, you can lose weight with less calorie counting and exercise.
Unfortunately, despite the hype, marketing and celebrity testimonials, ramping up your metabolism is mostly a myth.
“To make a long story short, there is very little hope of changing your resting metabolic rate, because you’re fighting your biology,” says Eric Ravussin, director of the Nutrition Obesity Research Centre at the Pennington Biomedical Research Centre in Baton Rouge, Louisiana.
To understand why trying to speed up your metabolism is mostly a waste of time and money, let’s start with some physiological facts.
You might read that you can pump up your metabolism by getting enough sleep to keep your appetite hormones in check or by lowering your stress level so that your body doesn’t produce too much cortisol, which can lead to overeating
Your resting metabolic rate 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 are mistakenly used interchangeably.)
Resting metabolic rate
A resting metabolic rate (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.
RMR plays an obvious role in weight: If the sum of someone’s daily calories consumed minus calories burnt 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. Susan Roberts, director of the energy metabolism lab at the Jean Mayer USDA Human Nutrition Research Centre on Ageing at Tufts University, says the difference can be about 10 per cent in each direction. A typical 35-year-old woman who is 1.67 metres and weighs 63 kilograms will typically have a resting metabolic rate equal to about 1,500 calories a day, while other similar women might need only 1,350 calories (10 per cent less) or 1,650 calories (10 per cent more).
Kevin Hall, section chief of the National Institute of Diabetes and Digestive and Kidney Diseases’ Integrative Physiology Section, says part of the reason for different rates can be attributed to internal variations.
“Some organs use more energy than others,” he says. “A person with a large liver can have a higher metabolic rate.”
Differences in brain size can also play a role.
Issue of genetics
Finally, there’s the issue of genetics.
Ravussin, who has conducted extensive research on Pima Indians, found family membership to be a significant factor in explaining differences in resting metabolism among people of similar size and body composition.
These factors explain why “revving up” your metabolism is, mostly, a doomed quest, akin to striving to be taller or to have greener eyes than what’s in your genetically prescribed range.
Not only is speeding up metabolism unlikely, but the methods that claim to do so also either don’t work or won’t create lasting results.
For example, you might read that you can pump up your metabolism by getting enough sleep to keep your appetite hormones in check or by lowering your stress level so that your body doesn’t produce too 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.
Similarly, while higher-intensity workouts might result in a slight post-workout afterburn (research conflicts on this issue), those short-term results don’t affect what your metabolism will be the following day.
Supplement makers tout ingredients such as green tea, caffeine, capsaicin, selenium and more, either individually or in, as one company puts it, a “thermogenic fat-burning complex,” as metabolism boosters.
Drinking a lot of water has long been a staple of weight-loss programmes, in part because doing so makes you feel fuller.
Some research has found that extra water consumption can also increase your resting metabolic rate. Roberts says there are two dietary tweaks that can increase metabolism because they increase the body’s energy needs for digestion: eating more fibre and protein.
She advises a diet that includes 25 to 35 grams of fibre per day and in which protein constitutes 25 to 30 per cent of calories. As with drinking water, the potential payoff is modest — fewer than 100 extra calories burnt per day for most people.
As for exercise, increasing your muscle mass will slightly boost your resting metabolism. Note that 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. A better approach: Do heavy resistance training to slow the rate that you lose muscle mass beginning in your late 30s or early 40s. Holding on to as much muscle as you can with age will keep your metabolism higher.
While you can’t really speed up metabolism, you can, unfortunately, slow it.
A more realistic and healthy goal than trying to accelerate your metabolism is trying to keep it as high as possible. The steps you can take in pursuit of that goal align with practices that are good for both health and weight maintenance: Avoid large swings in weight, stay active, drink enough water, eat enough fibre and protein, build muscle when young and maintain the muscle as you age. You can’t control your biology, but you can control your choices.
Or, as Ravussin puts it: “The average person is 25 pounds heavier than in the 1980s. It is not our genes that have changed.”
— Washington Post
Scott Douglas is a columnist and the author of several books, including “The Athlete’s Guide to CBD.”