"One study is never enough to change a recommendation,
but this study is interesting in that it shows that a
low-fat diet is no better than a low-carbohydrate
diet in preventing type 2 diabetes," said
Thomas Halton, lead author of a study in the current issue
of the American
Journal of Clinical Nutrition. "The one
diet that did seem to show a protective effect was a vegetable-based,
low-carb diet which consisted of higher amounts of vegetable
fat and vegetable protein, and lower amounts of carbohydrate."
The findings, Halton added, were a bit surprising in
that most doctors and nutritionists recommend a low-fat
diet to prevent type 2 diabetes. "This study showed
that a low-fat diet didn't really prevent type 2 diabetes
in our cohort when compared to a low-carb diet. I was
also surprised that total carbohydrate consumption was
associated with type 2 diabetes, and that the relative
risk for the glycemic load was so high."
Halton is a recent graduate of the Harvard School of
Public Health and has founded his own nutrition consulting
company, Fitness Plus, in Boston.
Type 2 diabetes, which is associated with overweight
and obesity, is a pressing health problem around the world.
In the United States, two-thirds of adults weigh more
than they should.
And, according to background information in the study,
some 45 percent of women and 30 percent of men in the
United States are trying to lose weight at any one time.
While low-fat, high-carb diets are often recommended,
the long-term effects of such a regimen are not known.
People who reduce their carb intake generally take in
more total and saturated fat and less whole grains, cereal
fiber, fruit and vegetables, which can heighten the risk
of type 2 diabetes.
For this study, Halton and his colleagues examined the
association between low-carb diets and the risk of diabetes
among 85,059 women participating in the Nurse's Health
Study. The data included 20 years of follow-up.
Women were ranked according to what they ate. "We
calculated a low-carbohydrate diet score based on the
women's percent consumption of fat, protein and carbohydrate,"
Halton explained. "A higher score reflected a higher
intake of fat and protein and a lower intake of carbohydrate.
Therefore, the higher a woman's score, the more closely
she followed a low carb-diet, and the lower her score,
the more closely she followed a low-fat diet."
Women with a higher score did not have a heightened risk
of diabetes. In fact, they seemed to have a small decreased
risk when they derived their fat and protein from vegetable
rather than animal sources.
Such a low-carb diet is similar to a healthy Atkins diet,
meaning one which does not include large amounts of animal
fat and animal protein, Halton said.
"When focusing on vegetable sources of fat and protein,
this version of Atkins is similar to a low-glycemic Mediterranean
diet," he said.
How easy will it be for people to follow such a diet?
"It's probably a very good thing to do . . .
[but] people don't understand how to eat well. People
don't know what simple and complex carbohydrates are
and what it takes to have a good, balanced diet. People
go to extremes," said Dr. Stuart Weiss, a clinical
assistant professor of medicine at New York University
School of Medicine in New
York City. "In general, carbs should be limited
just like saturated fat needs to be limited. . . If you
eat too much of anything, you're bound to get into