Research paper
Rolls BJ, Roe LS, Meengs JS. The effect of large portion sizes on energy intake is sustained for 11 days. Obesity (Silver Spring). 2007 Jun;15(6):1535-43. doi:10.1038/oby.2007.182. PMID:17557991
Why we cite it
A controlled crossover study in 23 normal-weight and overweight participants (10 women, 13 men; BMI 22.9 ± 0.8 women, 24.6 ± 0.8 men, Table 1) finding (corrected 2026-09-19 from ”mean BMI 25.6″, a figure from the library’s restatement that matches neither group nor the paper) that the portion size effect on energy intake is sustained over 11 days — participants did not compensate for the excess over that period. Extends an earlier 2-day finding to 11 days. The authors conclude, hedged, that the results ”strengthen the evidence suggesting that increased portions contribute to the overconsumption of energy and to excess body weight”. A non-Wansink portion size study (see kwr01). (Corrected 2026-09-19 from ”to show that large portions represent a durable driver of overeating, not a novelty effect” and ”one of the key”: the first dropped the authors’ suggesting … contribute, and the second is a ranking.)