The easy availability of large portions of relatively energy-dense foods may contribute to the increasing prevalence of obesity in the U.S. In an article published in the American Journal of Clinical Nutrition, Rolls et al. studied the effects of portion size on overall food intake. They concluded that large food portions typically served in American restaurants or self-service during family meals may significantly affect the risk of obesity.
The 51 men and women who participated in the study, aged 21-40 years, were not trying to either gain or lose weight. They initially completed 4 questionnaires to determine whether they usually exercised self-restraint in the presence of large portions of food. On each test day, they were fed a test lunch that included a macaroni and cheese entrée. Twenty-seven participants received the entrée on individual plates (“plate group”) in varying portions from small to large, and the other 24 subjects served themselves as many helpings as they desired (“serving dish group”). Five members of each group were identified as “plate cleaners” who consumed the entire portion of each serving. Both men and women ate more in response to a larger portion size, though females overall consumed an average of 30% less food than males did. Less than one half of the men and women reported noticing any difference in the portion sizes they were served at meals. The authors suggest that people have the expectation that the amount of food served to them by others is appropriate, and that strategies to limit portion sizes in restaurants or at home should be developed in order to stem the national obesity epidemic.
Rolls, Barbara J et al. Portion size of food affects energy intake in normal-weight and overweight men and women. Am J Clin Nutr 2002;76:1207-13.