Fat: Underrated, Understand?

WHEN YOU THINK of fat, you probably think of foods that have a lot
of fat—or people who do. After a few years with some extra
pounds, the only thing you know about fat is that you’re tired of
it and want to get rid of it forever. But it’s probably one of your
body’s most misunderstood dietary nutrients, stemming from a
widely held but misguided belief that fat should take much of the
blame for our obesity epidemic.
In the 1980s, the U.S. government released nutritional guidelines
that essentially said we should base our diets on potatoes,
rice, cereal, and pasta and minimize the foods with a lot of fat and
protein. That gave way to the idea that fat makes you fat. And
that gave way to a new breed of diets that said if you limit the fat
in what you eat, you’ll limit the fat that exercises squatter’s rights
on your gut. But that line of thinking didn’t hold out when researchers
tried to find links between low-fat diets and obesity. In
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1998, for example, two prominent obesity researchers estimated
that if you took only 10 percent of your calories from fat, you’d lose
16 grams of fat a day—a loss of 50 pounds in a year. But when a
Harvard epidemiologist, Walter Willett, tried to find evidence that
this occurred, he couldn’t find any link between people who lost
weight and the fact that they were on a low-fat diet. In fact, in
some studies lasting a year or more, groups of people showed
weight gains on low-fat diets. Willett speculated that there was a
mechanism responsible for this: When the body is on a low-fat diet
for a long period, it stops losing weight.
Part of the reason our bodies rebel against low-fat diets is that
we need fat. For instance, fat plays a vital role in the delivery of vitamins
A, D, E, and K, nutrients stored in fatty tissue and the liver
until your body needs them. Fat also helps produce testosterone,
which helps trigger muscle growth. And fat, like protein, helps
keep you satisfied and controls your appetite. In fact, if we’ve
learned anything about weight loss over the past several years, it’s
that reducing your fat intake doesn’t necessarily do a darn thing
to decrease your body fat. One small study, for instance, compared
a high-carbohydrate diet and a high-fat diet. The researchers
found that the group with the high-fat diet experienced less muscle
loss than the other group. The researchers theorized that muscle
protein was being spared by the higher-fat diet because fatty acids,
more so than carbs, were being harnessed and used for energy.
The truth is that reasonable amounts of fat can actually help
you lose weight. In a study from the International Journal of Obesity,
researchers at Boston’s Brigham and Women’s Hospital and
Harvard Medical School put 101 overweight people on either a
low-fat diet (fat was 20 percent of the total calories) or a moderatefat
diet (35 percent of calories) and followed them for 18 months.
Both groups lost weight at first, but after a year and a half, the
moderate-fat group had lost an average of 9 pounds per person,
whereas the low-fat dieters had gained 6 pounds. The results sug-
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gest that a healthy amount of fat is a factor in keeping your weight
under control.
Here’s a primer on the fats in your life.
Trans fat: BAD. You won’t find trans fatty acids listed on most
food labels, even though there are more than 40,000 packaged
foods that contain this type of fat. You won’t find it listed because
it’s so bad for you that food manufacturers have fought for years
to keep it off ingredient labels. In 2003, the U.S. Food and Drug
Administration finally adopted regulations requiring manufacturers
to include trans fat content on their packaging, but the regulations
will be phased in over the next few years. For now, you
have to be a smart food consumer to spot where the danger lies.
Trans fats were invented by grocery manufacturers in the
1950s as a way of appealing to our natural cravings for fatty foods.
But there’s nothing natural about trans fats—they’re cholesterolraising,
heart-weakening, diabetes-causing, belly-building chemicals
that, for the most part, didn’t even exist until the middle of
the last century, and some studies have linked them to an estimated
30,000 premature deaths in this country every year. In one
Harvard study, researchers found that getting just 3 percent of
your daily calories from trans fats increased your risk of heart disease
by 50 percent. Three percent of your daily calories equals
about 7 grams of trans fats—that’s roughly the amount in a single
order of fries. Americans eat an average of between 3 and 10
grams of trans fats every day.
To understand what trans fats are, picture a bottle of vegetable
oil and a stick of margarine. At room temperature, the vegetable
oil is a liquid, the margarine a solid. Now, if you baked cookies
using vegetable oil, they’d be pretty greasy. And who would want
to buy a cookie swimming in oil? So to create cookies—and cakes,
nachos, chips, pies, muffins, doughnuts, waffles, and many, many
other foods we consume daily—manufacturers heat the oil to very
high temperatures and infuse it with hydrogen. That hydrogen
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bonds with the oil to create an entirely new form of fat—trans
fat—that stays solid at room temperature. Vegetable oil becomes
margarine. And now foods that might normally be healthy—but
maybe not as tasty—become fat bombs.
Since these trans fats don’t exist in nature, your body has a hell
of a time processing them. Once consumed, trans fats are free to
cause all sorts of mischief inside you. They raise the number of LDL
(bad) cholesterol particles in your bloodstream and lower your HDL
(good) cholesterol. They also raise blood levels of other lipoproteins;
the more lipoprotein you have in your bloodstream, the greater
your risk of heart disease. Increased consumption of trans fats has
also been linked to increased risk of diabetes and cancer.
Yet trans fats are added to a shocking number of foods. They
appear on food labels as PARTIALLY HYDROGENATED OIL—usually vegetable
or palm oil. Go look in your pantry and freezer right now,
and you won’t believe how many foods include them. Crackers.
Popcorn. Cookies. Fish sticks. Cheese spreads. Candy bars. Frozen
waffles. Stuffing. Even foods you might assume are healthy—like
bran muffins, cereals, and nondairy creamers—are often loaded
with trans fats. And because they hide in foods that look like
they’re low in fat, such as Wheat Thins, these fats are making you
unhealthy without your even knowing it.