Penn State diet studies: To weigh less, eat more

University Park, Pa. -- Two new Penn State studies show that people who pursue a healthy, low-fat, low-energy-density diet that includes more water-rich foods, such as fruits and vegetables, consume more food but weigh less than people who eat a more energy-dense diet.

Barbara Rolls, who holds the Guthrie Chair of Nutrition in Penn State's College of Health and Human Development, directed the studies. She says, "In one of the studies, we looked at the eating patterns of 7,500 men and women who constituted a representative sample of American adults. In the other study, 101 obese women were counseled to increase their intake of water-rich foods and to select reduced-fat foods rather than full-fat ones. In both cases eating more low-energy-dense, water-rich foods, such as fruits and vegetables, was associated with lower body weights.

"Decreasing the energy density of your diet by choosing more low-energy-dense foods, such as fruits and vegetables, can be a successful strategy to lose weight without counting calories or fat grams," she adds.

Both studies were detailed Nov. 17, at the annual meeting of the North American Association for the Study of Obesity in Las Vegas, Nevada.

Jenny H. Ledikwe, postdoctoral fellow in nutritional epidemiology, conducted the study in which she looked at the diet patterns of 7,500 typical Americans. She calculated the average daily energy density of their intake using two 24-hour recalls from the 1994-96 U.S. Department of Agriculture Continuing Survey of Food Intakes by Individuals. She then compared the participants with low, medium and high energy density (ED) diets.

Ledikwe found that despite the fact that the people in the low energy density group ate a greater weight of food than those in the high energy density group, they consumed fewer calories and weighed less. She notes, "Individuals who ate low-fat, high-fiber diets rich in fruits and vegetables weighed less, consumed more food and had healthier eating patterns."

Julie Ello-Martin, doctoral candidate in nutrition, conducted the study in which women were counseled. In this study, 101 obese women were divided into two groups. One group, the energy density (ED) group, was counseled to eat more water-rich foods and to choose fat-reduced foods as ways to lower the energy density of their diet. The second group, the reduced-fat (RF) group, was counseled with more restrictive messages focusing on eating less fat and limiting portions.

The women in both groups received individual counseling for six months and a follow-up period of six additional months of individual and group counseling. No calorie or fat gram goals were assigned in either group. The women could eat whatever they wanted while following the principles they learned in their counseling sessions.

After the first six-month period, the women in the ED group had lost 21 pounds while the women in the RF group had lost only 15 pounds.

The women in the ED group also significantly lowered the energy density of their diet versus the RF group but there was no difference in fat intake.

Ello-Martin says, "This is the first long-term study to look at how a low energy density diet can affect body weight. It's important because it shows that a healthy diet pattern can result in significant weight loss without couting calories or fat grams."

Ello-Martin's co-authors are Liane Roe, research nutritionist, and Rolls. The study was supported by a grant from the National Institute of Diabetes and Digestive and Kidney Disease.

Ledikwe's co-authors include Rolls and the following nutritional epidemiologists from the Centers for Disease Control and Prevention: Heidi M. Blanck, Laura Kettel Khan, Mary Serdula, Jennifer D. Seymour, and Beth C. Tohill. The study was supported by grants from the National institute of Diabetes and Digestive and Kidney Diseases, and an appointment to the Research Participation Program at the Centers for Disease Control and Prevention, Division of Nutrition and Physical Activity administered by the Oak Ridge Institute for Science and Education.