You Are Now Entering the (Twilight)
Zone
For: Protein—Striking a Balance, May 2002
It's difficult to follow a sensible weight-loss diet
or, for some people, even a heart-healthy, weight-maintenance diet. And
therein lies the secret of many a best-seller. Contrarian diets that question
common sense and mainstream science usually fall into one of two categories:
the Spartan, magic-bullet diet ("eat just grapefruit and lose weight")
or the experts-are-all-wrong diet that promises to manipulate body chemistry
and allow you to thrive and grow slim on steak and ice cream, or martinis
and bacon.
The most popular entry now in the contrarian category is The
Zone (and subsequent books) by Barry Sears, with its scientific-sounding
spin. Sears blames the policies of the American Heart Association (AHA)
for the epidemic of obesity in the U.S. and for cardiovascular disease.
He claims that cardiovascular deaths are increasing because Americans
are eating the heart-healthy diets recommended by the AHA and others.
This is doubly untrue. Cardiovascular deaths have been declining for years
and still are, and most Americans are not following a heart-healthy diet.
Other Zone claims are also vague, elusive, and
misleading.
The diet Sears recommends is not really radical: 40% of
its calories come from carbohydrates, 30% from protein, and 30% from fat.
The AHA and the WELLNESS LETTER recommend half that much protein and considerably
more carbohydrates. (Many faddish diets over the years have recommended
even higher amounts of protein.) But Sears claims that his diet will somehow
elevate you into a mystical place called "the Zone." Fluctuating
insulin levels, rather than calories, make you fat and decrease energy,
he says. In the Zone your insulin levels will remain stable and you'll
feel great and energetic.
But let's look at this and other claims.
Claim:
"Trendy low-fat, high-carbohydrate diets" are keeping people
fat. In the Zone diet you "use fat to lose fat."
The facts:
Most Americans still eat a lot of fat, protein, and increasing
amounts of sugars (which are one type of carbohydrates, to be sure). "Trendy
low-fat, high-carbohydrate diets" must mean those like the Dean Ornish
and Pritikin plans, designed for people who already have heart disease,
in which only 10% of calories come from fat. But very few people are eating
this way. And when they do, they usually lose weight. It would be impossible
to "use fat to lose fat" since fat contains more than twice
as many calories by weight as carbohydrates or protein.
Claim: Eating fat doesn't
make you fat. It's your body's response to excess carbohydrates
that does it. Carbohydrates boost your insulin production, which in turn
causes you to store carbohydrates as body fat.
The facts: Anything you eat
can make you fat if the calories add up. You gain weight when you eat
more calories than you burn, whether the calories come from protein or
carbohydrates. Moreover, not all carbohydrates cause insulin levels to
rise rapidly. These levels fluctuate normally. There is no evidence that
high insulin levels, whether temporary or sustained, make you fat.
Claim: It's hard to lose
weight by restricting calories.
The facts: Yes, indeed. But
when you look closely at The Zone, you find plain old calorie restriction,
as in any other weight-loss diet. Sears recommends three meals a day averaging
500 calories each, plus two snacks of 100 calories each. That's 1,700
calories a day—which would indeed produce weight loss in most people
and also leave them hungry. Most of his menus call for meat three times
a day (ham, Canadian bacon, chicken), but in small amounts.
Claim: The rise in insulin
caused by a low-fat, high-carbo-hydrate diet makes you produce more bad
eicosanoids than good ones. The imbalance of good and bad eicosanoids
means disease. Everything from heart disease to arthritis and multiple
sclerosis can be blamed on bad eicosanoids.
The facts: There's no
evidence for this wild claim. Eicosanoids are hormones and hormone-like
substances that play some role in many bodily processes. Few of them are
well understood by anyone, including Barry Sears. His biochemical claims
sound impressive, but are unfounded and oversimplified. What is clear,
however, is that fruits, whole grains, and vegetables—all of them
rich in complex carbohydrates and fiber—are the best foods you can
eat if you want to reduce the risk for hypertension, heart attack, diabetes,
and cancer. Very low-fat or almost no-fat diets such as Pritikin and Ornish
can indeed reverse the buildup of plaque (atherosclerosis) in the coronary
arteries.
Claim: "Unfavorable"
carbohydrates, which boost insulin a great deal, include carrots, brown
rice, mango, banana, butternut squash, lima beans, and sweet potatoes.
The facts: All carbohydrate-rich
foods temporarily boost blood sugar, and thus insulin production, to some
extent. Foods that have the greatest effect on blood sugar are said to
have a high glycemic index. Sears's list of "unfavorables"
is odd—some with a high glycemic index (carrots), some not (lima
beans). In any case, there's no evidence that such foods cause weight
gain. Many of these foods are very nutritious—even diabetics can
eat them in moderation.
Claim: The Zone diet can reverse
cancer, heart disease, and multiple sclerosis, and is also a treatment
for AIDS.
The facts: There's no
evidence for this. Such claims create false hopes for sick people.
If weight loss is your goal, the Zone plan might help you get started, since it is low in calories and includes exercise. But this is not a lifelong eating plan. It won't reduce your risk for chronic diseases. And one particularly serious problem with "zoning" is that the foods Sears recommends are low in fiber. Indeed, his diets average only about 8 grams of fiber a day. Fiber not only reduces the risk of colon and possibly other cancers, but it also improves control of blood sugar and promotes bowel regularity. As with other high-protein diets, constipation in the Zone would be a potential problem.
Words to the wise: Eat a diet
based largely on fruits, whole grains, and vegetables. If you are a healthy
person trying to stay that way, aim to get about 60% of your calories
from carbohydrates, 30% or less from fat (with less than 10% from saturated
fat). That leaves 10 to 15% for protein—plenty for anyone. Choose
nonfat or low-fat dairy products. Do aerobic exercise regularly. If you
need to lose weight, consume fewer calories and exercise more—you've
heard it before. "The Zone" is a zone where you don't need
to go.
UC Berkeley Wellness Letter, June 1998
