
Some Starchy Foods May Contribute to
OvereatingBy Judy
McBride March 1, 1999WASHINGTON, March 1--Meals high in carbohydrates that are rapidly
digested and absorbed appear to trigger a series of hormonal and metabolic
changes that promote overeating in obese people, according to a new study at a
U.S. Department of Agriculture research
center. The study findings are published in the March issue of Pediatrics.
These findings provide the first solid evidence that carbohydrates are
one piece of the puzzle in determining what makes some people overeat,
Agriculture Secretary Dan Glickman said. Scientists use the term high glycemic index (GI) to describe
carbohydrates that are rapidly digested and absorbed. The Boston researchers
conclude that high GI meals set off a chain of actions that cause people to
overeat. On three separate days, a week or more apart, researchers fed a group of
obese teenage boys breakfast and lunch with a high, medium or low glycemic
index. Then they measured changes in the boys blood glucose, fatty acids
and insulin and other hormones for five hours after breakfast. Blood glucose
and insulin rose highest and fastest after the high GI breakfast. Within a few
hours, however, blood glucose and fatty acids dropped significantly, triggering
a stress response, indicated by a rise in the hormone adrenalin. After the boys consumed an identical lunch, they were encouraged to select
what they wanted from a platter of foods when they felt very
hungry. The subjects ate nearly twice as much after a high GI meal than
after a low-GI meal. About one-fifth of U.S. children and one-third of adults are now
significantly overweight, despite a significant drop in fat intake in recent
years. Researchers David S. Ludwig at
Children's Hospital of Boston
and physiologist Susan B. Roberts at the
USDA Human Nutrition Research Center on
Aging at Tufts University believe that the results likely apply to the
middle-aged and elderly as well. According to Roberts, high GI foods include refined grain products and
potatoes, as well as sources of concentrated sugars, such as sodas and fruit
juices. Some starchy foods have higher GIs than table sugar. Moreover, many of
the low-fat foods that have flooded grocery shelves are also high in calories.
Vegetables and fruits generally have a low GI. Roberts said the findings do not support weight-loss diets based entirely on
the glycemic index because many low-GI foods, including steak, butter and ice
cream, are high in calories. These low-GI foods trigger overeating because they
are palatable and calorically dense. Ludwig, who directs the obesity program at Childrens Hospital, said GI
has a role in weight regulation along with genetics, physical activity,
psychological factors and other dietary variables. Scientific contact: Susan B. Roberts, PhD,
Energy
Metabolism Laboratory, USDA Human Nutrition Research Center on Aging at
Tufts, Boston, Mass., phone (617) 556-3238,
[email protected]; or
David S. Ludwig, M.D., PhD, The Childrens Hospital, Boston, Mass., phone
(617) 355-4878, [email protected]. Story contacts Human Nutrition Research Center on Aging U.S. Department of Agriculture | |