This paper selectively reviews available evidence concerning psychological characteristics associated with obesity, psychological changes accompanying very-low-calorie diets (VLCDs), and the influence of certain psychological factors on response to VLCD treatment. The obese population as a whole does not show an elevated incidence of psychopathology. Treatment-seeking obese do show more psychiatric disturbance, at a level comparable to other medical/surgical patients. There appear to be no global personality traits or profiles that are associated with obesity. However, obese people differ from non-obese groups on psychological and behavioral variables related to weight and eating and more frequently display perceptual and emotional body image anomalies. Binge eating appears rather common among obese groups. VLCDs have generally neutral to positive effects on hunger, depression, and anxiety. New data on body image suggest that VLCDs are associated with post-treatment underestimation of body size. Finally, recent data on possible psychological and behavioral correlates of VLCDs outcome are presented.