there has been one standard answer for overweight people: you
eat too much, or you exercise too little, or both. Doctors, nutritionists
and dietitians all echo the "party line". Well, it simply
isn’t true! There are people who get fat easily and people who
remain skin and bones no matter how much they eat or how little
they exercise. Not only can two people differ radically in their
tendency to get fat, but the same person can change radically
in his lifetime. Women who take birth control pills often gain
more easily. The party line would be that they started to eat
more or exercise less, but thousands of women claim the contrary.
approach to overweight can be shown by a drawing of a water tank.
Water is added to the tank by a faucet above and let out of the
tank by a faucet below. Humans are supposed to be just like this
tank. Increasing the flow from the upper faucet is like eating
more calories; when you do, the level in the tank goes up. Closing
the lower faucet is like decreasing your daily exercise; the level
of fat in your body goes up. Well, this analogy is partly true
– getting fat is largely a matter of eating too much and exercising
too little. Unfortunately, the analogy breaks down under practical
everyday experience because it implies that people are passive
reservoirs, affected only by outside food supply and exercise.
is, we are not passive reservoirs or tanks, but active metabolizing
machines, each different, each handling calories differently.
I prefer to think of the body as a machine that runs efficiently
or inefficiently, depending on circumstances. Just as an automobile
may be tuned up properly to get more mileage from its fuel, the
human machine also can become more efficient.
One of the
unique features of the human machine is that it has two fuel tanks:
one tank for sugar or, more technically, glucose and one for fat.
Wouldn’t it be neat if our cars were built that same way? Anytime
we ran out of gasoline, we’d just switch over to our diesel fuel
tank. Actually, in our bodies, we don’t switch back and forth
from one fuel to another; we use both simultaneously.
people are unaware that 60-70 percent of the energy muscles need
when one is resting is supplied by fat. That is, fats,
either from a recent meal or from fat deposits, travels through
the blood to muscle where they contribute more than half of the
resting muscle’s energy needs. Glucose and fats are burned side
by side all day long, but fats supply most of the energy.
fat is therefore a natural body function. The trouble is, fat
people’s bodies are overly proficient at storing fat and are less
than normally proficient at burning it.
with the tank of water doesn’t hold completely, because some people’s
body machine work harder to store fat than other people’s. It
isn’t simply a matter of "you eat too much or your exercise
unlike the analogy with the water tank, being fat tends to make
you get even fatter. Fatness is a viscous cycle; the more fat
you have, the more your body chemistry, or metabolism, changes
to favor the buildup of even more fat.