Can you re-set your metabolism?
There are over 16 million answers to that question on Google—and most of them say that you can either re-set, supercharge or outright hack your metabolism. And, of course, none of these bio-hacks give advice on how to slow it down. Nobody wants a slower metabolism.
The dream of having a faster metabolism is pervasive, since so many blame our inability to lose weight on a sluggish metabolism. Some of Google’s links lead to sites that promote green tea, eating spicy foods or cooking with coconut oil as ways to boost our internal energy-burning engines. There are also no shortage of supplements, diet books, eating regimens and workout programs, all designed to help you hit the reset button.
Do any of them work? We caught up with Dr. Arya Sharma, professor of medicine at the University of Alberta, Edmonton, and leading global authority on obesity, to ask him this burning question. We started with resistance exercise, since fitness gurus often advise bulking up, based on the idea that muscle burns more calories than fat.
“Muscle mass does burn calories even when it’s not doing anything, but this still only amounts to a small amount of the total ‘resting metabolic rate’ so it won’t make a lot of difference,” said Sharma. “And it’s really hard to build muscle, so this idea that, you know, ‘I’m just going to bulk up and that’s going to make me burn calories in my sleep,’ doesn’t really work, because it doesn’t have a huge impact on your actual ‘resting metabolic rate.’”
Our “resting metabolic rate” or “basal metabolic rate” (BMR) refers to the calories our bodies need to burn just to stay alive. It takes a certain amount of energy to regulate our body temperature, keep our blood circulating and maintain our organs, including the tissues — both muscle and fat. Muscle is more “metabolically active,” meaning that, even when we’re at rest, muscle burns through more calories than fat (roughly three times more). Unfortunately, only 15 per cent of our BMR is devoted to keeping tissues alive and the other 85 per cent is spent regulating our heart, brain, liver, kidneys, lungs et cetera, so converting a little fat to muscle doesn’t do much to move the needle.
The BMR, however, isn’t the only component of our overall metabolism—only the most important part.
“The basal metabolic rate is the biggest chunk of calories the average Canadian burns,” continued Sharma. “It’s about two-thirds of your daily calories, or about 1,400 calories per day for the average person. And those are the calories you burn just sitting in your chair or lying in your bed. So the majority of your daily caloric requirements is just to sustain life.”
The rest? Sharma divides the remaining third of our energy expenditure into two categories — activities of daily living and “intentional exercise.” The first refers to the low-level physical activity we engage in when we putter around the house, climb a set of stairs or walk around the grocery store. And most of us expend more energy doing “unintentional exercise” than we do on proper “intentional exercise.” No matter what impression we might get from social media, Canadians just don’t get a lot of exercise.
“Other than that, there is a very small amount of calories that get burned just digesting your food,” he added. (It depends on what you eat and how often, but it’s roughly 10 per cent of your caloric intake.)
All these together make up our “metabolism” — the total number of calories we burn. And, since two-thirds of our calories are burned while we’re at rest, the BMR is what most booster schemes are hoping to impact.
“The problem is that it’s very difficult to change our resting metabolic rate, because you can’t change the number of calories that your brain needs or your heart needs or your kidney needs or all your internal organs need,” says Sharma. “That’s a pretty fixed number that doesn’t change very much.”
Except, it turns out, as we age. Sadly, it changes in the wrong direction. Every birthday, we need at least 10 fewer calories per day than we did the year before. That might not sound like much but it adds up to hundreds of calories over decades. For post-menopausal women, that number might be even higher, since hormonal changes can effect metabolism. Some pregnant women also experience metabolic change — also in the wrong direction.
“There are no tricks, really, except if you’re looking for ways to slow your metabolism down,” said Sharma. “The best way to do that is to lose weight, because, every time you lose weight, your metabolism actually does slow down for all kinds of different reasons.”
And the main reason there, Sharma explained, is simply that our bodies resist weight loss.
“The whole problem with weight loss is that bodies don’t like to lose weight,” he said. “So anytime you try to trick your body into losing weight, it doesn’t matter how you do it, your body fights you. Your metabolic rate goes down and you actually become more fuel- efficient so that your body runs on fewer calories.”
This, obviously, is the problem with “yo-yo dieting” — each time you lose weight, your BMR drops a little more. Sharma warned that any diet that advertises a metabolic “trick” is likely one you have to be on for the rest of your life in order to avoid gaining back the weight. And the more restrictive the diet, the less realistic that is.
So, the answer is no. Or, as Meghan Trainor might put it, no to the ah, to the, no, no, no.
That might sound like sad news, but the good news is that we can give up fad diets and just focus on the basic principles of healthier living, starting with eating more high-fibre foods, including fresh fruits and vegetables, less meat (especially fatty meat) and fewer processed foods. Add to that some more intentional exercise and getting more steps in and you’re in business.
“That’s pretty much the best advice,” Sharma said. “The healthiest approach is to try to eat as balanced a diet as you can, making sure there’s everything in your diet that your body needs and to be as physically active as you can. I mean, that’s healthy advice but that’s not just for controlling weight, that’s for having a healthy body no matter what size you are.”