Portion size of food affects energy intake in normal-weight and overweight men and women.

“BACKGROUND:
Large portions of food may contribute to excess energy intake and greater obesity. However, data on the effects of portion size on food intake in adults are limited.

OBJECTIVES:
We examined the effect of portion size on intake during a single meal. We also investigated whether the response to portion size depended on which person, the subject or the experimenter, determined the amount of food on the plate.

DESIGN:
Fifty-one men and women were served lunch 1 d/wk for 4 wk. Lunch included an entrée of macaroni and cheese consumed ad libitum. At each meal, subjects were presented with 1 of 4 portions of the entrée: 500, 625, 750, or 1000 g. One group of subjects received the portion on a plate, and a second group received it in a serving dish and took the amount they desired on their plates.

RESULTS:
Portion size significantly influenced energy intake at lunch (P < 0.0001). Subjects consumed 30% more energy (676 kJ) when offered the largest portion than when offered the smallest portion. The response ...