Study Finds Health Benefit
in Low-Glycemic Diet
A diet rich in the type of carbohydrates
that maintain a more stable blood sugar beats out a conventional
low-fat diet in reducing the risk factors for heart disease and
diabetes, according to a new study.
Researchers compared a diet rich
in carbohydrates with a low glycemic index -- the type that stabilizes
blood sugar -- with a conventional low-fat diet that included
carbohydrates with a high glycemic index.
"Carbohydrates with a low glycemic
index are absorbed through the small intestine and converted to
blood sugar at a much slower rate than high glycemic, resulting
in a more stable blood sugar and much less insulin being produced,"
said Mark A. Pereira, a University of Minnesota epidemiologist.
"So that would help prevent or control diabetes."
The work by Pereira and his team
appears in the Nov. 24 issue of the Journal of the American
In the study, those on the low-glycemic
diets also achieved better improvement in blood pressure and blood
fats, and their resting metabolic rate -- the rate at which the
body burns energy or calories at rest -- didn't drop as much as
it did for those on the low-fat diet.
Pereira and his colleagues assigned
39 overweight or obese young adults, ages 18 to 40, to either
the low-glycemic diet or the low-fat one. The low-glycemic diet
got 43 percent of calories from carbohydrates, 27 percent from
protein, and 30 percent from fat, Pereira said.
(For the sake of comparison, the
popular Zone diet consists of 40 percent of calories from carbohydrates,
30 percent from protein, and 30 percent from fat. Low-glycemic
carbohydrates are recommended.)
Those on the low-fat diet got 65
percent of their calories from carbohydrates, 17 percent from
protein, and 18 percent from fat. Both diets were restricted in
calories to achieve a 10 percent weight loss.
Food was provided for the subjects.
The low-glycemic menus featured such foods as steel-cut oatmeal,
barley and whole-grain breads. The menus for the low-fat diet
included carbohydrate foods with a higher glycemic index, such
as instant oatmeal, white bread and white rice.
Pereira's team measured blood pressure,
insulin resistance (a predictor of diabetes), blood fats and other
risk factors for diabetes and heart disease, before and after
the weight loss. "Generally, what we found across the board for
blood fats and blood pressure and insulin resistance is, the decrease
with weight loss was twice as great for the low-glycemic group
compared to the low-fat group."
Both groups averaged the same amount
of weight loss, the 10 percent goal, but the dieters on the low-glycemic
diet reported less hunger. And their resting metabolic rate, which
typically drops during weight loss, dropped less in the low-glycemic
"For the conventional low-fat dieters,
the metabolic rate slowed down by 175 calories a day," Pereira
said. "For the low-glycemic group, there was a 95-calorie drop."
The new study echoes those of previous
studies, Pereira added.
Meanwhile, another expert said
it's difficult to credit the low-glycemic diet for the results.
"I think it's a very interesting
study," said Alice Lichtenstein, a spokeswoman for the American
Heart Association and professor of nutrition, science, and policy
at Tufts University. "However, whether the effect is due to glycemic
load or to a higher low-fat diet can't really be distinguished."
She's referring to the fact that the low-glycemic menus allowed
more fat -- about 30 percent -- than the low-fat, which allowed
18 percent fat.
"Certainly, a number of studies
have shown that low-fat diets are not optimal for promoting weight
loss or decreasing cardiovascular risk," she added. The low-glycemic
diet studies may be better because it is moderate fat, she said.
Lichtenstein cautioned that people
trying to lose weight and reduce disease risk should not become
too obsessed with total fat or glycemic load at the expense of
calories. The most important aspect is watching "total calories
and increasing activity," she said.
articles on Glycemic Index.
Reference Source 101
November 30, 2004