August 25, 2005

Environment Plays Major Role In Diet

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At a barbeque in Collegetown, Dan Lee ’07 picked up his third hamburger from the grill. “I’m not very hungry,” he admitted. “But it looks really good.”

Lee, like most other people, may use environmental rather than biological cues to decide how much food to consume, according to a Cornell study published in the April 2005 edition of Physiology and Behavior. In the study, 12 normal-weight men and women overate for 13 days, during which they consumed about 35% more energy than they would in normal meals. Although the participants gained an average of five pounds, they did not attempt to shed the extra weight afterwards by eating less. Instead, during the three-week recovery period, they resumed their normal level of food intake.

According to David Levitsky, the study’s principal researcher and a professor of nutritional science and psychology, the results contribute to the hypothesis that external cues, such as portion size and the number of other people eating, are the primary influences on how much a person eats.

“The majority of my colleagues believe that eating behavior is very closely linked to our biology. Our genetics determine the amount of body fat we will have … This argues in a very pessimistic way that you can’t change your body fat,” Levitsky said.

“There is an alternative view — which I have been pushing for several years — that says our body weight is a function of our environment. Our environment determines our behavior,” he said.

Eva Obarzanek Ph.D. ’84, a co-author of the study who is now a nutritionist for the National Institutes of Health, pointed to the rising number of overweight people as support for Levitsky’s alternative view.

“There’s a tremendous increase in obesity that maybe has doubled. That’s not due to changes in internal mechanisms or physiological changes,” she said.

Interestingly, although the 12 subjects did not exercise or curb their eating afterwards, they still lost about half the weight they had gained in the study.

“You burn more energy simply by carrying around additional weight,” explained Levitsky, according to the Cornell News Service. “The spontaneous increase in metabolic rate that we found in the subjects after overeating was remarkably consistent with a comparable overfeeding study in animals, as well as with other studies with humans and overeating.”

The researcher’s advice for healthy eating is to “be cognizant of the food cues that are inducing you to eat. Secondly, be very sensitive to portion sizes.”

“Watch your weight; weigh yourself frequently … Skip a meal every once in a while until you get back to where you should be,” he added.

Along with Levitsky and Obarzanek, Gordana Mrdjenovic ’00 and Prof. David Levitsky, nutritional sciences, were the other co-authors of the study.

This fall, Levitsky plans to research the body’s reaction to energy deficits when meals are skipped.

Archived article by Xiaowei Cathy Tang
Sun Senior Editor