|
By
Nanci Hellmich
The Atkins low-carb,
high-fat diet is supposed to be simple, but it's raising complex
medical and nutrition questions. Now two new studies show
that those who follow the diet can lose significant amounts
of weight, but other research is raising concerns about the
safety of the program, linking it to an increased risk of
kidney stones and bone loss. Fueled by recent media attention
and reports of successful weight loss, Dr. Atkins' New Diet
Revolution by cardiologist Robert Atkins, is No. 1 on USA
TODAY's Best-Selling Books List.
First published
in 1972, the diet allows dieters to consume steak, hamburger,
pork, butter, cheese and other high-fat foods and has them
cut way back on carbohydrates including pasta, sweets, some
starchy vegetables and many fruits. Some of the nation's leading
obesity researchers and nutritionists are outraged by the
diet, arguing that it runs contrary to the advice of most
major health organizations, which advocate a diet relatively
low in saturated (animal) fat and high in complex carbohydrates
(grains, vegetables).
Those recommendations
are based on scientific evidence that a diet rich in fruits
and veggies and low in saturated fat reduces the risk of heart
disease, some types of cancer and other health problems. Still,
many dieters swear by the Atkins diet. And until recently,
there haven't been many studies investigating its safety and
effectiveness.
In one new study
conducted at Duke University Medical Center and funded by
a grant from the Robert C. Atkins Foundation, participants
ate a very low carbohydrate diet of 25 grams a day for six
months. They could eat an unlimited amount of meat and eggs,
two cups of salad and one cup of low-carbohydrate vegetables
such as broccoli and cauliflower a day. Of the 50 patients
enrolled, 80% adhered to the diet for the entire study, losing
an average of 10% of their original body weight.
The average weight
lost was approximately 20 pounds, says Eric Westman, associate
professor of medicine at Duke University Medical Center. The
Atkins dieters also had improvements in blood cholesterol
and triglycerides, but researchers don't know if those changes
are due to losing weight, cutting back on junk food or the
makeup of the diet.
In another pilot
study, obesity researchers at three universities recruited
63 people who were 30 or more pounds overweight and assigned
them to one of two programs. One group was given a copy of
Dr. Atkins' New Diet Revolution. The other group was put on
a conventional diet with about 30% of calories from fat, 55%
from carbohydrates and 15% from protein.
At the end of six
months, those following the Atkins diet lost about 10% of
their starting weight and those on the conventional diet lost
about 5%. Atkins dieters also were more likely to stick with
the plan than conventional dieters. The Atkins program "may
give people a way to eat fewer calories," says lead researcher
Gary Foster, clinical director of the Weight and Eating Disorders
Program at the University of Pennsylvania School of Medicine.
He says researchers
don't know if the benefits of losing weight outweigh the drawbacks
of eating a diet high in saturated fat. There is nothing miraculous
about the Atkins diet, but if you put people on a low-calorie
diet, they lose weight, says Keith Ayoob, a spokesman for
the American Dietetic Association. "It's the number of
calories, not where they come from." Foster and fellow
researchers are going to continue to investigate the Atkins
diet with a longer-term study sponsored by the National Institutes
of Health.
They will look
at several different aspects, including whether the diet may
be more useful for some people than others and how much people
are able to exercise while eating a low-carb diet. They also
want to investigate why some dieters seem more likely to stick
with the Atkins program than a more conventional diet.
One theory suggests
that people on the Atkins diet may eat less because of a loss
of appetite due to ketosis, a state in which the body partially
breaks down body fat, producing organic compounds called ketones
as fuel. This is due to the limited carbohydrates. Colette
Heimowitz, an Atkins spokeswoman, says the latest version
of the diet book puts less emphasis on ketosis because people
may not have to be in this state to lose weight on the program.
She says people
don't get as hungry because the fat in the plan has a positive
impact on blood sugar and insulin, and protein makes people
feel full longer. But other experts say these theories are
unproven and need further investigation because hunger is
complex.
Westman of Duke
says people may get positive reinforcement from losing weight
fast on Atkins, which keeps them going. Or this diet really
may appeal to people who prefer to eat this way. "There
are some meat lovers, and on this kind of diet you can eat
a lot of meat," he says. "Still, we need more research
to determine the safety of the diet." Some researchers
have concerns about several medical issues.
According to a
study by researchers at the University of Texas Southwestern
Medical Center in Dallas, the Atkins diet may increase the
risk of kidney stones and bone loss. For this study, 10 healthy
subjects ate a regular diet for two weeks, then for two weeks
they followed a highly restrictive, Atkins-based diet that
included some vegetables but no fruits and 20 grams or less
of carbohydrates a day.
The participants
then ate a less restrictive form of the diet for the final
four weeks. Based on blood and urine tests, researcher Chia-Ying
Wang concludes that "there was an increased risk of developing
kidney stones and a possible increase in the risk of bone
loss." The findings are reported in the August American
Journal of Kidney Diseases. "We think the diet's combination
of low carbohydrates and high animal protein results in sufficient
acid to increase the risk for certain kinds of kidney stones,"
she says.
Heimowitz says
studies of six months show there is an adaptation to the program
without any kidney stone formation or bone loss. But she agrees
with the researchers that those following the diet should
take a multivitamin and drink adequate water. The food composition
of the Atkins plan continues to trouble many experts. "You
don't eat just to get thin," says Barbara Rolls, a nutrition
professor at Pennsylvania State University.
"You eat a
good balanced variety of foods and nutrients for a lot of
other reasons, which have to do with cardiovascular health,
cancer protection, bone health." Rolls and Ayoob wonder
whether most people who lose weight on the diet will keep
the weight off long-term by eating this way. "Do people
really want to give up bananas and their favorite fruits?"
Ayoob asks. Says Rolls, "You can achieve weight loss
in lots of different ways. The real challenge is to figure
out a way to keep it off."
USA
Today August 6, 2002
American
Journal Kidney Disease August 2002;40(2):265-74
| 