Dr. Barbara Rolls, who holds the Guthrie Chair of Nutrition in Penn State's College of Health and Human Development, directed the study. She says, "We lowered the energy density, or calories per gram, of the participants' meals by incorporating more vegetables and fruit in recipes and also using food products reduced in fat and sugar. The subjects found the smaller, lower energy density meals just as palatable, filling and satisfying as the big, high calorie menu items -- and they didn't compensate for lowered intake on the first day by eating more on the second day of the study."
Rolls detailed the study results Monday, Nov. 15 at the annual meeting of the North American Association for the Study of Obesity (NAASO) in Las Vegas. Her co-authors are Liane Roe, research nutritionist, and Jennifer S. Meengs, research technologist.
In the study, on two consecutive days in each of four weeks, 24 young women, ages 19 to 35, ate breakfast, lunch and dinner in Penn State's Laboratory for the Study of Human Ingestive Behavior. They also received evening snacks to take home.
The same two-day menu was served in all weeks but the foods were varied in energy density and portion size. The meals were either standard or reduced by 30 percent in energy density or reduced 25 percent in portion size or both.
Reducing the energy density of foods by 30 percent led to a 23 percent decrease in daily calorie intake. Reducing the portion size by 25 percent led to a 12 percent decrease in calorie intake. Despite the large variation in intake, there were no significant differences in ratings of hunger or fullness over the two days.
Rolls notes, "This study shows that even small reductions in the energy density or portion size of foods are likely to decrease energy intake. The results suggests that home cooks and restaurants could take an easy step toward obesity prevention by adding more fruits and vegetables and trimming the fat to decrease energy density without having to serve tiny portions."
Reducing energy density is the key to Rolls' eating plan and the subject of her best-selling book, The Volumetrics Weight-Control Plan. In March 2005, Harper Collins will publish The Volumetrics Eating Plan, a new cookbook and lifestyle guide based on Roll's research. The new guide will contain menu planners, charts and sidebars on healthy food choices, 44 color photographs, and 125 recipes that translate Rolls' research into practical advice.
Photos are available at http://www.psu.edu/ur/2004/foodphotos.htm