The clinical literature has long acknowledged the paradoxical findings that deliberate attempts to suppress particular thoughts actually increase their occurrence. The unwanted, intrusive thoughts that are a major feature of obsessive disorders, depression, sleep disorders, and a range of other disturbances are of particular clinical concern. The exploration of psychological factors associated with cognitive control is, therefore, clinically relevant. The present paper considers the role of mental control and thought suppression in bulimia nervosa in explaining the occurrence of unwanted thoughts and feelings, specifically in relation to weight, shape, and food. Our fundamental argument is that suppression of thoughts of food, weight, and body shape can lead to the increased frequency of these thoughts. The increase in unwanted thoughts is likely to result in a loss of control over eating, and lead to the escalation and perpetuation of bulimia. Dietary restriction is likely to be associated with successful suppression, and binge-eating with failed suppression. Indeed, the initial success of suppression paradoxically causes its inevitable failure. We conclude that the suppression of thoughts of food and weight or shape in bulimia nervosa is maladaptive and counterproductive. In addition, the therapeutic implications of thought suppression are considered.