The buddy system: A randomized controlled experiment of the benefits and costs of dieting in pairs.

A total of 67 pairs of female roommates were randomized into a diet condition: (1) both ate normally; (2) one dieted, the other ate normally; and (3) both dieted. Adherence, weight loss, anxiety, depression, disordered eating symptoms, and stress were measured. Dieters lost more weight than non-dieters, but average loss was <1 pound.