1
YOUR METABOLISM IS IN
EVERY CELL IN YOUR BODY.
A lot of people talk about their metab-
olism like it’s a muscle or organ they
can somehow control. But in reality,
the term refers to a series of chemical
processes in each cell that turn the cal-
ories you eat into fuel to keep you alive.
“It’s the culmination of different
tissues with different needs and how
many calories it takes to keep them
functioning,” says Michael D. Jensen,
a physician-scientist who studies obes-
ity and metabolism at the Mayo Clinic
in Rochester, Minn.
The body’s major organs—the brain,
liver, kidneys and heart—account for
over half of the energy burned at rest,
while fat, the digestive system and
especially the body’s muscles account
for the remainder.2
MOST OF THE ENERGY
YOU BURN IS FROM YOUR
RESTING METABOLISM.
There are three main ways you burn
energy: a) the basal metabolism, which
is the energy used for your body’s basic
functioning while at rest; b) the energy
used to break down food, also known
as the thermic effect of food; and
c) the energy used in physical activity.
One very underappreciated fact
about the body is that your resting
metabolism accounts for a huge
amount of the total calories you burn
each day. Physical activity, on the
other hand, accounts for a tiny part ofyour total energy expenditure—about
10 to 30 per cent (unless you’re a pro-
fessional athlete or have a highly phys-
ically demanding job). Digesting food
accounts for about 10 per cent.
“It’s generally accepted that for
most people, the basal metabolic rate
accounts for 60 to 80 per cent of total
energy expenditure,” says Alexxai
Kravitz, a neuroscientist and obesity
researcher at Washington University
in St. Louis.
“It’s not nothing, but it’s not nearly
equal to food intake,” Kravitz added.
“This is why it’s not so surprising that
exercise leads to [statistically] signifi-
cant, but small, changes in weight.”3
METABOLISM CAN VARY
A LOT BETWEEN PEOPLE,
AND RESEARCHERS DON’T
UNDERSTAND WHY.
It’s true that two people with the same
size and body composition can have
different metabolic rates. One can con-
sume a huge meal and gain no weight,
while the other has to count calories.
But why this is remains a “black
box,” says Will Wong, a researcher and
professor at the Johns Hopkins Univer-
sity Center for Metabolism and Obesity
Research, in Baltimore. “We don’t
understand the mechanism that con-
trols a person’s metabolic rate.”
Researchers have been able to find
some predictors of how fast a person’s
metabolism will be. These include: the
amount of lean muscle and fat tissuereader’s digest
56 september 2019