Research paper
Rolls BJ, Morris EL, Roe LS. Portion size of food affects energy intake in normal-weight and overweight men and women. Am J Clin Nutr. 2002 Dec;76(6):1207-1213. doi:10.1093/ajcn/76.6.1207
Why we cite it
Reports that the portion size effect on energy intake was not influenced by sex, BMI, or dietary restraint scores — the abstract's own wording — in 51 men and women, within-subjects. That is a failure to detect moderation, not a demonstration that none exists. Uses the same macaroni-and-cheese paradigm as cpi17 (children) but with adults, providing complementary evidence across age groups. Establishes portion size as a modifiable environmental determinant of energy intake.