Being overweight or obese are medical conditions that are very difficult to treat. There is compelling evidence that obesity is commonly seen in patients with schizophrenia. Recently, a number of publications have focused on the ability of atypical antipsychotic drugs to induce obesity. All antipsychotic drugs produce weight gain, but their potential varies. Many studies overwhelmingly confirm that atypical antipsychotic drugs produce substantially more weight gain in comparison with typical antipsychotic drugs. Clozapine and olanzapine have the most weight-inducing potential. Even ziprasidone, which is considered to be weight neutral, produces weight gain in some patients. The pathophysiology of weight gain is complicated. Many neurohormones, neuropeptides and intestinal hormones, as well as adipose tissue and hair root-derived hormones, interact with environmental factors to produce weight gain. The basis of weight-gain treatment is an understanding of the etiology. Drug-induced obesity provides a unique opportunity to psychiatrists to understand this true psychosomatic problem. In the absence of this knowledge, prevention is the best hope. Education, diet control and simple behavioral measures may prevent excessive weight gain. In those with weight gain, treatment can be attempted with pharmacotherapy.