Package unit size and amount of food: Do both influence intake?

Objective: Large portions increase intake and are hypothesized to contribute to the obesity epidemic. However, it is unclear if portion size affects intake through changes in the unit size of available food or the overall amount of food available for consumption. Thus, this study examined the independent effects of package unit size and amount of food on intake. It was hypothesized that both variables would influence intake. Research Methods and Procedures: Non-obese (BMI <30 kg/m(2)), non-smoking, unrestrained, college-aged men (n = 12) and women (n = 16) who regularly consumed (>= 3 times/wk) snack foods were randomly assigned to one of four groups crossing package unit size (small vs. large) and amount of food (small vs. large). Participants were given a box with 4 snack foods (potato chips, cheese crackers, cookies, and candy) packaged according to their assigned group to take home and eat over 3 days. Dependent variables were energy and gram intake of provided snack foods. Results: An effect of amount of food was found (p < 0.01). A 100% increase in the amount of food provided produced an 81% increase in energy consumed from the snack foods [small amount, 21,037.6 +/- 10,852 kJ (5028 +/- 2596 kcal) vs. large amount, 11,640.7 +/- 4914.1 kJ (2782 +/- 1174 kcal)]. No effect of package unit size was found. Discussion: These results suggest that the amount of food available to eat strongly influences intake.