Environmental effects on the intake of overweight and normal-weight men.

The effects of changes in portion size and social condition on food intake were compared for overweight and normal-weight men. Subjects believed they were participating in a luncheon test of the acceptability of lasagna. In Study 1, under conditions designed to mimic social dining in a cafeteria, subjects were given either 255 or 426 g of lasagna. All subjects at a particular session received the same size portion and could ask for as many helpings as they wished. While overweight subjects ate more than normal-weight subjects, changes in portion size had no significant effects on intake. In Study 2, the effects of social vs. isolated dining were compared. Overweight subjects ate more than normal-weight subjects, and both overweight and normal-weight subjects eating socially ate more than subjects eating alone. In both studies there was a significant relationship between preference rating and intake for overweight subjects but not for normal-weight subjects. The results support the existence of differences in intake between overweight and normal-weight individuals and also indicate the potential importance of environmental factors in the intake of both groups.