Obese as likely as lean women to feel full on low energy density meals

October 29, 2000

University Park, Pa. ---In a recent eating study at Penn State, obese women were just as likely as lean women to hardly notice when they ate 450 calories less - as long as their meals contained lots of fruits, vegetables or grains to bulk up the servings and lower the energy density or number of calories per ounce.

Four hundred and fifty calories less a day are enough to enable someone to lose as much as a pound a week. Yet, despite this large reduction in calories consumed when they were served the low energy density meals, the women reported only slightly more hunger (7 percent) and slightly less fullness (5 percent) after eating. There was no difference in the ratings by obese and lean women.

"These results offer further evidence that adopting a low energy density approach to eating can make it easier to manage your weight," says Elizabeth A. Bell, doctoral candidate in nutrition, who conducted the study as part of her dissertation research.

Bell will present her results Monday, Oct. 30, in a paper, "Energy Density Influences Energy Intake Across Varying Levels of Fat Content in Both Lean and Obese Women," at the North American Association for the Study of Obesity annual meeting in Long Beach, Calif. Her co-authors are Liane S. Roe, research nutritionist, and her dissertation adviser, Dr. Barbara Rolls, who holds the Guthrie Chair in Nutrition in Penn State's College of Health and Human Development.

The researchers also looked at the effect of the fat content of the meals. As in previous studies conducted by Rolls' research group, the study showed that the fat content of the meal didn't influence how much the participants ate or how satisfied they felt.

Rolls says, "We've seen repeatedly in our studies that people eat about the same amount of food each day and, if they consume less than they are used to, they feel hungry. Fat can make food taste good but it doesn't necessarily make you feel full. Eating the portion size or volume of food that you usually do is the key to feeling satisfied."In the current study, 17 obese and 19 lean women, ages 18 to 45 years, spent 12 hours one day each week for six weeks at the Penn State Laboratory for the Study of Human Ingestive Behavior where they ate all of their meals and an evening snack. The meals and snacks offered were either low or high energy density and the fat content was kept in ranges typical of the American diet, either 25 percent of calories from fat, 35 percent or 45 percent. The women were free to eat as much as they wanted of all of the entrees.

During each of the six sessions, meals included the following, along with small side dishes: cheese strata for breakfast, taco salad for lunch, pasta with cheese and veggies for dinner, and warm apple crisp for the evening snack. The low energy density versions of these entrees were prepared, for example, by substituting vegetables and fruits for some of the bread, pasta or other grain products and by using low fat versions of the high fat ingredients. Differences in appearance, taste and texture of the entrees were hard to detect and the women reported that they liked the entrees across all conditions.

When the women were served the low energy density meals, they ate about 450 calories less than when they were served high energy density meals even though their portion sizes remained about the same as when they ate the high energy density versions. They didn't feel excessive hunger. In short, they felt full on fewer calories.

Bell notes, "These results show, once again, that people don't have to restrict portion sizes and, in some cases, may even be able to eat more if they reduce the energy density of their meals."

"If you reduce fat content, you also usually reduce energy density. However, it's not safe to assume that every reduced fat food is also reduced in calories," she adds. "It's also important when selecting foods to pay attention to the energy density, the number of calories per ounce, as well as the fat content."

Information on the energy density of foods and how to lower the ratio of calories to the weight of food in meals can be found in the best selling book, "Volumetrics," co-authored by Rolls. Now available in hardback, the paperback version will be out in December. "Volumetrics" is available wherever books are sold.

Volumetrics, based on Rolls' research program, outlines, in layman's language, how and why feeling full depends on eating a satisfying amount of food. It details how foods high in water, such as broth-based soups or foods rich in fruits and vegetables, as well as foods puffed-up with air, can aid weight management. In addition, it contains information that can help individuals learn how to stop eating when they're no longer hungry, make smart choices during social meals and eat normal portions.
EDITORS: Elizabeth Bell and Dr. Barbara Rolls can be reached by calling the Laboratory for the Study of Human Ingestive Behavior (814) 863-8482 or via e-mail at eab149@psu.edu for Bell and bjr4@psu.edu for Rolls.

Penn State

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