Modeling of food intake among restrained and unrestrained eaters

The Theory of Normal Eating suggests that how much others eat sets an upper limit for how much it is appropriate to eat. This study tested the hypothesis that restrained eaters, who typically eat less than they want to, would be more responsive to a high-intake norm than would unrestrained eaters. Data were combined from 8 experimental studies (total N = 735 female participants; 305 restrained eaters, 430 unrestrained eaters). Each study: (a) included a low-intake norm, a high-intake norm, and a no-norm control condition; (b) measured participants' food intake; and (c) included the Restraint Scale as a measure of dietary restraint. There were no differences between restrained unrestrained eaters in the no-norm control condition or in the magnitude of the inhibition effect (i.e., the difference between the low-intake norm condition and the control condition). There was, however, a restraint difference in the magnitude of the augmentation effect (i.e., the difference between the high-intake norm condition and the control condition). Restrained eaters showed a larger augmentation effect (d = 0.58; 95% CI = 0.29, 0.87) than did unrestrained eaters (d = 0.20; 95% CI = -0.05, 0.45). Social norms provide an upper limit for acceptable food intake, with high-intake norms permitting (but not requiring) individuals to indulge themselves. The fact that restrained eaters were more responsive to the high-intake norm than were unrestrained eaters suggests that the high-intake norm gives restrained eaters permission to indulge when they typically eat less than they want to.