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.