A number of ethical issues must be considered in the treatment of clients who are dissatisfied with their weight. Current societal attitudes of opprobrium toward fat affect psychologists as well as the general public, and may have deleterious effects on our ability to provide competent, responsible, and respectful help to large clients, particularly women. Psychologists should be aware that weight status has a large biogenetic component and that dieting is remarkably ineffective in producing long-term weight loss. Professionals tend to overestimate the harmful effects of obesity and underestimate the negative impact of dieting on physical and psychological functioning. We propose that psychologists accept diversity of body size as a manifestation of human differences, promote overall health over thinness, and help clients become self-accepting instead of self-depriving.