Turning Off the Fat Genes

“It doesn’t make any difference what I eat. Weight problems just
run in my family. It’s all genetic.” These are common excuses,
but genetic research has just shot them down in flames.

Genes do influence our size and shape, but studies clearly show
that if you change your diet and lifestyle, you can override
hereditary effects to a great degree. Contrary to popular
understanding, genes are not dictators; they are committees.
They do not give orders; they make suggestions. You can
counteract your fat genes and boost your thin genes.

We often think of genes as unchangeable because, when it comes
to eye color or hair color, they really are decisive. If they
call for blue eyes or brown hair, that’s it. But the genes that
establish your size and shape are much more flexible. They need
to be able to adjust your appetite and your calorie burning,
depending on whether food is plentiful or not, and whether you
are working hard or resting. Unlike eye or hair color, your body
has to be able to change its composition from minute to minute,
from day to day.

Although your chromosomes are extraordinarily complex, there are
just five key gene groups you need to know about:

* Taste genes determine the foods you crave. In taste
experiments, scientists use a test substance called PROP
(6-N-propylthiouracil). About one in four people can taste its
bitterness very strongly. These people avoid grapefruits and
never go near black coffee. Although their acute taste sense is
generally an advantage, the downside is they may avoid healthy
vegetables, such as broccoli or cabbage, that have a hint of
bitterness. If this group includes you, you’ll want to find ways
to flavor these healthy vegetables so you will include them in
your routine.

Another one in four people cannot taste PROP and are called
“taste blind.” Their problem is they may tend to overeat, making
up in quantity what they are missing in taste. If this includes
you, and you tend to be indiscriminate in what you’re eating,
you’ll want to take care to emphasize fruits, vegetables, whole
grains, and beans, and to be very cautious about fatty foods and
their hidden calories.

* A gene on chromosome 7 makes leptin, the appetite-taming
hormone. In 1997, English researchers reported the case of two
cousins who became extremely obese very early in life. They
demanded food continuously and ate much more than their
siblings. At age 8, one weighed 189 pounds. She had so much
trouble walking she had to have liposuction of her legs. Her
cousin was only two years old but already weighed 64 pounds. It
turned out they shared a rare mutation blocking the leptin gene.
With no leptin to curb hunger, their appetites were voracious.

You are not likely to have this same gene abnormality. However,
your leptin may not be working perfectly either.
Very-low-calorie diets disrupt its appetite-taming effect,
causing your appetite to run out of control. The key to keeping
leptin working right is to avoid severe calorie restrictions. If
you eat at least 10 calories per day per pound of your ideal
weight, you are unlikely to run into serious problems.

* A gene on chromosome 8 builds LPL, the key enzyme that stores
fat in your cells. It waits along the walls of the tiny blood
vessels that course through your body fat, and its job is to
extract fat from your bloodstream and pass it into your fat
cells for storage. If your LPL is doing its job a little too
well, you can change this genetic tendency by choosing foods
that have little or no fat in them. Once again, vegetables,
fruits, legumes, and whole grains are your best friends.

* The hormone insulin, coded on chromosome 11, is part of your
body’s system for increasing your metabolism after meals.
Depending on the type of foods you choose, you can help insulin
spark a pronounced after-meal burn that releases calories as
body heat rather than storing them as fat. Low-fat, vegan diets,
along with regular exercise, make insulin more efficient.

* Believe it or not, exercise aptitude is largely biological,
too. People who love to go for a five-mile run at the crack of
dawn are genetically different from other people. They are
endowed with a better capillary network that brings oxygen to
working muscles and a more efficient fuel-burning mechanism. If
you did not get these genetic advantages, you can do the next
best thing. If you begin a regular exercise program and stick
with it, your muscle cells begin to look more and more like
those of natural athletes.

There is no need to be daunted by your family heritage. Yes,
some of us will always be bigger and others smaller. But with a
healthy, low-fat diet and regular physical activity, your genes
can stop working against you and start working for you.

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