"Anorexia nervosa is an eating disorder defined by a symptomatic triad, anorexia, emaciation and amenorrhoea. This disease mainly affects young women. Besides these three symptoms, hyperactivity is often associated with anorexia nervosa. Hyperactivity can be considered as a strategy to lose weight, but studies on animal models have shown that it could be explained by more complicated mechanisms. Hyperactivity is defined by an excess of physical activity, which can induce social, professional and family consequences. Hyperactivity can take different forms, most striking is the restless one. Patients with anorexia nervosa are not all hyperactive. Brewerton et al. have compared patients with anorexia nervosa and hyperactivity to patients without hyperactivity. Hyperactive patients are more dissatisfied by their body image, they use less means of purging (laxatives, vomiting), and they start starving earlier than patients without hyperactivity. Many factors can promote the emergence and maintenance of hyperactivity, especially social and cultural requirements, sports environment, family influences. Various models can explain the links between excessive exercise and anorexia nervosa. Epling and Pierce have exposed a behavioural model which shows how hyperactivity can lead to starvation, creating a self-maintained cycle. Eisler and Le Grande have described four models to explain the links between hyperactivity and anorexia nervosa. First, excessive exercise can be considered as a symptom of anorexia nervosa. It can also promote the development of eating disorders. Anorexia nervosa and hyperactivity can be a manifestation of an other psychiatric disorder. At least, hyperactivity can be a variant of anorexia nervosa, which has the same effects, as weight loss. Hyperactivity can also be considered as a kind of obsessive compulsive disorder. Hyperactivity and obsessive compulsive disorders actually share some clinical and neurochemical characteristics. An other model consists in comparing excessive exercise in anorexia nervosa to an addictive behaviour. Self-starvation exacerbated by hyperactivity can be considered as an addiction to endogenous opioid."