We often hear that exercise can help with weight loss by speeding up or boosting our metabolism. So is it true? Can we use exercise to control our metabolism?
[Body Stuff with Dr. Jen Gunter]
To answer that question, we have to first dig deeper into what metabolism is. No surprise, metabolism is really complex, and scientists and researchers are still discovering many new things about it. Very simply, metabolism is the set of chemical reactions in every cell of our body that harnesses energy to keep us alive.
So much of what happens in our bodies is metabolism, making new cells is metabolism, growing hair is metabolism, and converting food into energy is metabolism. The sum total energy of all the metabolic processes that occur throughout our body is measured in calories. And surprisingly, exercise is usually a small percentage of our daily calorie burn.
Unless you're a professional athlete, most of our calorie expenditure is accounted for by our basal metabolic rate. All the vital stuff we need to function, like having a heartbeat, growing hair, building cells and even blinking. That stuff takes up a big chunk of our energy. So can we hack this equation in some way? Can we use exercise to speed up our metabolism so we burn more energy? Can we burn even more calories? Not just doing burpees, but while we're growing an eyelash, than before?
The answer is no. First of all, this is a misunderstanding of what fast versus slow metabolism really indicates. There's no clear link between thinner people and fast metabolism, and the same goes for larger people and slow metabolism. In fact, if you look at the absolute numbers, people with larger bodies have faster metabolisms, meaning they burn more calories because larger bodies have more cells, which in turn are doing more to sustain the body.
Now, differences in metabolism between people with similar body sizes do exist, but the difference between fast metabolism and slow metabolism can be about 300 calories. That’s like two apples and a banana.
How fast our metabolism works is mostly genetic and related to body size, but there's also age. Our metabolic rate changes a few times over our lifespan. We start with the metabolic rate of an infant. Then there is a switch when we are toddlers, and then it’s pretty stable during adulthood to age 60, when it changes again.
Researchers evaluated the Hadza, a group of people in Tanzania who live a traditional hunter gatherer lifestyle. And yet, when you control for body size and age, they burn a similar amount of calories a day as an average American adult. It seems that calories out is a pretty fixed number, and it appears that our bodies have limits. If we exercise harder, at first we may expend more energy, but over time, our metabolism will find ways to conserve.
Here's what I'm getting at. The point of our metabolic system is to manage energy, not to manage weight. So if you read an article or hear a so-called expert inviting you to boost your metabolism, remember that’s just marketing speak rooted in a weight loss culture. And it just isn’t true.
