CHAMPAIGN, Ill. - Size matters when it comes to meal portions in weight-loss diets, according to researchers at the University of Illinois at Urbana-Champaign. And consuming convenient, nutritious frozen dinners may be a way to control portion size.
Research dietitians Sandra M. Hannum and LeaAnn Carson, who work in the laboratory of food science and human nutrition professor John W. Erdman, studied how two diet regimens resulted in weight loss in overweight and obese men. Their findings will appear in the journal Diabetes, Obesity and Metabolism. The study was placed online by the journal last month.
Subjects following the first of the diets ate a self-selected regimen based on the Food Guide Pyramid, a nutrition plan established by the U.S. Department of Agriculture in 1992. Subjects following the second diet ate two packaged entrées each day plus recommended servings from the food pyramid. Both diets contained about 1,700 daily calories with equal amounts of carbohydrates, protein and fat.
Subjects in the packaged-entrée group chose from 24 varieties of Uncle Ben's bowls, a brand of frozen entrées produced by Masterfoods USA of Vernon, Calif. Masterfoods provided the meals for the subjects and funded the study.
Prior to the study, subjects in both diet groups reported daily consumption of about 2,400 calories. Subjects weighed about 97 kilograms (214 pounds) with a body mass index (BMI) ranging from 26 to 42 kilogram per meter squared, which qualified them as overweight to obese.
Over the course of the eight-week diet, all subjects reduced their daily caloric intake to about 1,700 calories and lost weight. Many subjects reported their surprise in feeling satiated by the diets.
Subjects who followed the frozen-entrée diet lost more weight (7.4 kg or 16.3 pounds) compared with the subjects who made their own meals following the food pyramid (5.1 kg or 11.2 pounds). Also, the average BMI decrease was one unit greater in subjects following the frozen-entrée diet than subjects following the food-pyramid diet.
These findings replicate the researchers' findings in overweight and obese women, which were published in the March 2004 issue of the journal Obesity Research.
Hannum and Carson and their colleagues attribute the greater weight loss among the frozen-entrée eaters to the automatic portion control built into that diet, whereas subjects following the pyramid diet had to make their own meals. "The pyramid group had to figure out what to eat, and estimate how much they actually consumed," Hannum said. "There was much more room for error."
After the Illinois studies had finished, the USDA announced a new food pyramid, which allows people to customize their diets according to their age, gender and daily levels of physical activity. The greater complexity of the new pyramid may make this diet even more difficult for people to use, Hannum said.
Whether the participants maintain their new weight depends on whether they can maintain permanent diet changes, an ability that varies across individuals. The study succeeded by pointing many of its subjects in the right direction of portion control.
Because of busy lifestyles, many people eat at restaurants rather than take the time to cook at home. Research in other laboratories has shown that people tend to eat the amount of food that they are served, including large restaurant portions.
"Many of our subjects said that the study was the kick they needed to think about portion size," Hannum said.