Carbohydrates: A Bad Rap

WITH THE BEATINGS that carbohydrates have taken over the past
few years, it’s a wonder that bread isn’t protected by the Endangered
Species Act. Everywhere I look, I see people eating burgers
without buns, ordering spaghetti and meatballs—hold the
spaghetti—or bragging about their all-bacon-all-the-time diet.
While it’s clear that protein and fat have tremendous nutritional
benefits, it’s unfair—and unhealthy—to kick carbohydrates off the
dietary island.
With more and more evidence showing that a high-carbohydrate
diet helps promote fat storage (unless you run marathons), it’s
becoming more accepted that low-carbohydrate diets work in
helping people control weight. A 2002 study in the journal
Metabolism confirmed that very stance. Researchers at the University
of Connecticut found that subjects who ate only 46
grams of carbohydrates a day—about 8 percent of calories—lost
7 pounds of fat and gained 2 pounds of muscle in 6 weeks. And
they did it while downing a satisfying 2,337 calories a day. But
you can make a major mistake by eliminating carbohydrates entirely.
Many carbohydrates—like fruits, vegetables, whole grains,
and beans—help protect you against cancer and other diseases,
and some carbs contain nutrients like fiber, which helps you
lose and control weight.
Traditionally, the confusion about carbohydrates has centered
around finding ways to classify them and figuring out which ones
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are better for your body. It used to be that we thought of carbohydrates
only by their molecular structure—either simple or
complex. Simple indicates a carb with one or two sugar molecules—
things like sucrose (table sugar), fructose (in fruit), and
lactose (in dairy products). Complex carbohydrates are ones that
include more than two sugar molecules—like pasta, rice, bread,
and potatoes. The flaw is that you can’t generalize and say a carbohydrate
is good or bad for you based simply on its molecular
structure. For example, an apple contains nutrients and helps
keep you lean; sugar does not. Both are simple carbs, but they’re
hardly comparable in nutritional value.
Instead, the way to decide what carbohydrates are best for
you stems from how your body reacts to the carbohydrates chemically.
One of the tools that nutritionists use today is the
glycemic index (GI). The GI assigns numbers to foods that indicate
how quickly a food turns into glucose. High-GI foods—ones
that are quickly digested and turned to glucose—are generally
less nutritionally sound than low-GI choices.
Another term for glucose is blood sugar. The presence of sugar
in your blood causes your body to produce the hormone insulin.
Insulin’s job is to move the sugar you’re not using for energy out
of your bloodstream and store it in your body. Here’s where the GI
comes into effect: Foods with a high GI (like pasta, bread, white
rice, and Snickers bars) are digested quickly, flooding your bloodstream
with sugar. Insulin rushes in and says, “Whoa, what do I
do with all of this?” Whatever glucose isn’t immediately burned
for energy quickly starts getting stored as fat. What’s worse is
that if you eat a carb with a high GI in combination with fat—
bread with butter, for example—none of the fat you eat can be
burned for energy either, because your bloodstream is so flooded
with sugar. Insulin does such a good job of turning this new
blood sugar into fat, in fact, that soon your blood sugar begins
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to drop, and you know what that means: You’re hungry again.
If you eat a meal with a low GI (like a balanced dinner of
chicken, high-fiber vegetables, and brown rice), the food is digested
more slowly. Your blood sugar rises only incrementally, and
that slow digestion means that glucose is available as energy for
hours and hours. That means you have hours and hours to burn
off the blood sugar. Insulin doesn’t need to rush in and turn the
sugar into fat; it can use the sugar slowly for other construction
projects, like building and repairing muscle. Moreover, because
your blood sugar levels stay even, you don’t turn ravenously
hungry just a few hours after eating. You build more muscle, you
store less fat, you have more energy, and you keep your appetite
under control.