Most Metabolism Boosters Are BS
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Take a stroll into any nutrition store and
you’ll see displays
stacked to the ceilings with products that
claim to “boost” your metabolism.
Whether they’re marketed as “Metabol Burn”
or “VitaGainzzzz” or something equally
there’s one thing that they have in common:
They don’t really work.
Decades of research show that making any meaningful
change in your metabolism
is really hard to do, so a powder or pill
won’t turn you into a calorie burning machine.
Most supplements can’t really boost your
and the actual changes we can make to it are
Contrary to what the supplements might lead
you to believe,
metabolism isn’t just the ability to burn
off energy from food.
The actual claims are all over the place,
but in general when a product says it “boosts”
that’s code for burning more calories or
Using calories is a part of metabolism,
but even that process is affected by your
physiology, like enzymes and hormones.
When scientists talk about metabolism,
they use it as a broader term for all of a
cell or body’s processes.
Which is a pretty big concept, and not very
informative on its own.
So since that’s such a broad definition, researchers
usually break it down into smaller components.
The biggest slice of the metabolic pie is
something called basal metabolic rate,
or BMR, and it’s the energy your body uses
But even that comes with an asterisk.
True BMR is measured when the subject is at
rest, at a certain temperature,
not digesting food, and not pregnant, because
all of those things
can nudge your energy consumption one way
or the other.
Fun fact: growing a whole other human inside
of you changes your energy needs.
Furthermore, different parts of the body have
different metabolic rates.
Gram for gram, your kidneys and heart consume
the most calories,
followed by your brain and liver.
Towards the bottom of that list is muscle
But no one is advocating taking on an extra
kidney to try to raise your rate of calorie burn.
Instead, researchers focus on two tissues
that we can tweak: fat and muscle.
Fat, or adipose tissue, is one of the ways
your body stores energy long term,
so it makes sense that it doesn’t take a
lot of energy to store energy.
Muscle, on the other hand, has the opposite
When you exercise, it uses quite a bit of
energy and oxygen,
but even at rest, its caloric needs are higher
And sure enough, people with a higher proportion
of muscle mass
tend to have higher basal metabolic rates
than people with more fat mass.
That is, they burn more calories per gram
of body weight even when they’re resting.
Now the second slice of the metabolic pie is energy
used during exercise, but again, with an asterisk.
Yes, when you exercise, you use a few more
calories for a short period of time,
but even a thirty minute workout burns a pretty
small number of calories compared to your BMR.
So researchers also look at how exercise affects
something called resting energy expenditure,
which is just a more relaxed way to measure
overall metabolism than the super-specific BMR.
Multiple research groups have found that aerobic
whether it’s long and slow like riding a
or short bursts of intense exercise like sprinting,
all elevate metabolism temporarily after exercise.
Likewise, lifting weights also leaves you
with a slightly boosted metabolism after the workout.
And long term, those bulkier muscles are probably
what make the biggest difference in your metabolism.
One 2008 study on diet and exercise in overweight
women found that resistance training
allowed participants to keep their metabolisms
elevated even after the diet,
while the ones who just cut calories ended
up slowing their metabolisms.
But even if you’re not hitting the gym,
you still have the third slice of the metabolic pie:
non-exercise activity thermogenesis, which
makes for a neat acronym.
It encompasses all of your day-to-day, moving-around-but-not-exercising
like walking around the house, or doing the
dishes, or watering the plants.
That adds up to a good chunk of metabolism,
but it varies a lot depending on your lifestyle.
Now this last way our bodies burn calories
actually has a lot to do with how we eat calories.
It takes energy to digest, absorb, and get
rid of food,
so we call those calories the thermic effect
High-protein foods take a bit more work to
digest than others,
so your steak has a higher thermic effect
than a bag of chips.
But even something like ice water has a thermogenic
thanks to our bodies warming it up, which
Now, it’s easy to think of our meat sack
bodies as simple calorie-burning engines,
but metabolism happens at the cellular level,
which is where supplements might claim their
For instance, after eating and digesting a
piece of fruit,
the simple sugar glucose is released into
This is our bodies’ main energy currency.
But it still needs to get into the cell so that cellular
machinery can turn it into usable energy.
And it’s a big molecule by cell standards,
so it doesn’t just seep right in.
Which is why our bodies produce insulin,
a hormone that binds to receptors on our cells
and shuttles glucose inside of them.
Without insulin, we could still digest food
and get glucose into our bloodstream,
but we wouldn’t be able to process it into
energy since it couldn’t enter the cell,
which is exactly what happens in diabetes!
Your body either can’t make enough insulin,
or has trouble importing enough sugar into cells.
But glucose isn’t the only nutrient our
body uses for fuel.
And chances are that if a product is marketed
as a metabolism booster,
it’s concerned with one nutrient: fat.
Now, fat is utilized in a complex chain of
chemical events that I’m not gonna explain here.
But at rest, your body typically doesn’t
use fat for energy.
That’s supposed to be stored energy,
whereas the glucose that’s floating in your
blood is ready to use right away.
Before resorting to breaking down fat, your
body will typically tap
the stored glucose in your muscles and liver,
And to complicate things further, your body
never only uses fat or only glucose as a fuel source.
It’s a mixture of both.
So hopefully you’re starting to see that
your metabolism has lots of moving pieces to it,
and if a product says it can change your metabolism,
that’s a pretty bold claim.
Despite the lack of evidence backing them,
pharmacies still keep these products in stock,
even as some researchers have voiced concerns
about their safety.
These products are available over the counter,
at least in the US,
but they’re not regulated as tightly as
Now, there are a few ingredients that can
increase resting energy expenditure,
but that doesn’t mean a supplement will
boost your metabolism long term.
Like capsaicin, the same molecule that gives
red pepper its spiciness.
This ingredient has been used to suppress
appetite in the past,
but it can also increase energy expenditure
and shift your body towards burning fat.
It does this by kicking off a chain of events that
eventually stimulates the sympathetic nervous system,
which is the same system that’s activated
during the fight or flight response.
This part of your nervous system is responsible
for basic bodily functions
like regulating heart rate and basal metabolic
So when we see a chemical that stimulates
the sympathetic nervous system,
we generally associate that with an increase
When researchers looked into capsaicin,
they saw it activate a receptor called TRPV1,
which is an important part of fat oxidation.
And it might also help you process glucose
more efficiently by toning down
the inflammatory response often associated
When used according to protocol,
capsaicin has the potential to help you burn
an extra 50 calories a day;
that’s according to a literature review
published in 2012.
But whether you stick to protocol or not is
a whole different issue.
Whether or not the subjects actually followed
directions usually determined any metabolic results.
And as can be the case with diet and supplement
the dosage of capsaicin varies widely from
study to study.
Some studies used pure capsaicin capsules
as high as 150 milligrams,
while others sprinkled less than a milligram’s
worth of red pepper on someone’s food.
Surprisingly though, this is consistent with
how much variation there is in our diets.
The average capsaicin intake in Europe is
1.5 milligrams a day.
Meanwhile, in countries with spicier cuisines,
like India or Mexico, it’s anywhere from 25-200 mg.
Now another metabolism boosting ingredient
that’s present in most countries’ diets is caffeine.
There’s extensive data supporting caffeine’s
ability to raise energy expenditure,
and it’s not because it keeps you awake
and jittery all night.
Caffeine ends up stimulating the same sympathetic
but through a different mechanism than capsaicin.
It also has the ability to activate an enzyme
called lipase, which promotes the breakdown of fat.
And caffeine comes in many different forms,
from pills to candy bars to coffee.
And despite all the other ingredients that
manufacturers throw into energy drinks and
other caffeinated products,
caffeine seems to be the only one that does
anything useful for metabolism.
A 2014 article from the journal Obesity reported
that a commercially available energy drink
raised subjects’ energy expenditures, but
a regular mixture of water and caffeine did the same thing.
This suggests that all those other ingredients,
usually some B vitamins,
don’t have any noticeable effect in these
Plus, the increase in fat burning ability
might actually be canceled out if the caffeine
interrupts your sleep.
One study in 2013 gave a moderate dose of
to young men who didn’t normally consume
And while their resting energy expenditures
didn’t change, they got less sleep.
Caffeine might be one of the reasons that
our final ingredient,
green tea, is such a common ingredient in
metabolism supplements as well.
Green tea extract is exactly what it sounds
like: compounds taken from green tea.
That usually includes caffeine as well as
a group of chemicals called catechins.
In cell, animal, and human studies, researchers
increased resting energy expenditure after
giving subjects doses of green tea.
One study back in 2005 gave participants capsules
of EGCG, one of the green tea catechins,
with caffeine and saw an increase in energy
expenditure of about 180 calories.
But the metabolic claims don’t stop there.
Green tea supposedly helps bump up your fat
although there’s not a lot of direct evidence
in human studies to support it.
Supposedly, the catechins within green tea
inhibit an enzyme that
degrades neurotransmitters like dopamine and
And just like capsaicin and caffeine, this
means stimulation of the
sympathetic nervous system, which raises energy
But it’s also been implied from these studies
that long term green tea use
might change our gene expression towards a
slight bump in fat metabolism.
But again, we need more evidence from human
At the same time, we’re still trying to
work out details on how to use it.
There are trials where researchers gave green tea
extract to participants and saw no noteworthy results.
So all of these ingredients have some evidence
to back them up,
but there’s a big difference from experimental
conditions to how you use the products at home.
Ultimately, one of the best metabolism boosters,
other than increasing muscle mass,
is a totally free product that you won’t
see on any nutrition store shelves: sleep.
For decades, we’ve known that sleep deprivation
can impair metabolism.
And it does this by messing around with certain
hormones that control energy intake and storage.
Research published in 2010 hooked subjects
up to a steady drip of glucose overnight
and cut their sleep to four hours per night
for two nights,
and then had them sleep ten hours per night
for another two nights.
And they found that ghrelin, a hormone that
signals hunger, was increased by 28%,
while leptin, a hormone that signals fullness,
even after the participants got two nights
of make-up sleep.
This went along with an increase in appetite
rating as well,
which you’re probably familiar with if you’ve
pulled an all-nighter.
Plus, sleep deprivation harms your insulin’s
ability to respond to glucose.
So while you might think you’re more active
while you’re awake into the wee hours of the night,
you’re doing your metabolism
more harm than good.
So can those flashy products in nutrition
stores actually boost your metabolism?
Well, there’s some truth to their claims,
but clearly, it’s not that straightforward.
Some work in specific conditions, while some
may actually be dangerous in large amounts.
And obviously, if you’re thinking about trying any
of these things, check with your doctor first.
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