in the body, age and genetics (though
researchers don’t know why some
families have higher or lower meta-
bolic rates). Sex also matters, since
women with any given body composi-
tion and age burn fewer calories than
comparable men.
You can’t easily measure your rest-
ing metabolic rate in a precise way.
There are some commercially available
tests, but the best measurements come
from research studies that use expen-
sive equipment. However, you can get
a rough estimate of your resting meta-
bolic rate by plugging some basic vari-
ables, like age, height and weight, into
online calculators. These will tell you
how many calories you’re expected to
burn each day, and if you eat that
many and your weight stays the same,
it’s probably correct.4
ANOTHER THING THAT SLOWS
DOWN THE METABOLISM:
GETTING OLDER.
The effect happens gradually, even if
you have the same amount of fat and
muscle tissue. So if you’re 60, you’ll
burn fewer calories at rest than you did
when you were 20.
Jensen said this continual decline
starts in young adulthood—and why
this happens is another metabolism
question researchers haven’t answered.
“Why do your energy needs go down as
you age, even if you keep everything
else pretty much the same? That’s one
of the bigger mysteries.”5
YOU CAN’T REALLY SPEED
UP YOUR METABOLISM
FOR WEIGHT LOSS.
There’s a lot of hype around “speeding
up your metabolism” and losing weight
by exercising more to build muscle,
eating different foods or taking supple-
ments. But it’s a myth.
While there are certain foods—like
coffee, chili and other spices—that may
increase the basal metabolic rate just a
little, Jensen says the change is so neg-
ligible and short-lived, it would never
have an impact on your waistline.
Building more muscles, however,
can be more helpful. Here’s why: one
of the variables that affects your resting
metabolic rate is the amount of lean
body mass you have. At any given
weight, the more muscle on your body,
the higher your metabolic rate. That’s
because muscle uses a lot more energy
than fat while at rest.
So the logic is, if you can build up
your muscle, you’ll have a higher rest-
ing metabolism and will burn the fuel
in your body more quickly. But there’s
a caveat.
According to Michael Rosenbaum,
professor of pediatrics and medicine at
Columbia University’s Irving Medical
Center and a researcher in New York
who studies weight loss and metab-
olism: “If you have more muscle, it
burns fuel more rapidly. But that’s only
half the question.” If you do gain more
muscle and effectively speed up your
metabolism, “You have to fight therd.ca 57