Portion Size Effects on Body Weight:Free Living Setting

The study purpose was to evaluate the effects of portion sizes on body weight and energy intake in a free-living setting. 223 healthy adults were recruited from an urban worksite and randomized to one of four groups for a six-month period. The groups were: 1) 400 kcal box lunch; 2) 800 kcal box lunch; 3) 1600 kcal box lunch; or 4) no box lunch. Participants were required to pick up a box lunch every week day for six months. Control participants did not receive a box lunch and were instructed to eat their usual lunch. Participants were weighed and dietary intake measured at baseline, one, three and six months. It was hypothesized that at six months, participants in the 1600 kcal box lunch would gain more weight and have higher energy intake than those in the other groups.

400 kcal box lunch was delivered each weekday to each participant at the worksite for a six month period.

800 kcal box lunch was delivered each weekday to each participant at the worksite for a six month period.

1600 kcal box lunch was delivered each weekday to each participant at the worksite for a six month period.

box lunches of different portion sizes were provided to participants each weekday for six months. Portion size conditions were 440 kcal, 800 kcal or 1600 kcal.

Inclusion Criteria: : 1) age 18-60 yrs; 2) nonsmoker; 3) fluent in English; 4) not taking medications that affect appetite or body weight; 5) work at the medical complex full time, including during the lunch hours; 6) not allergic to the foods in the study lunches; 7) willing to eat the foods in the study lunches [examples were provided of the types of foods]; 8) not currently on a diet to lose weight; 9) no history of a diagnosed eating disorder; 10) not moving from the area during the next six months; 11) not currently taking part in another research study; 12) not currently pregnant, nursing or pregnant in the last 12 months. Exclusion Criteria: if the person does not meet the criteria above -