Aggressive and violent behaviour is a challenging psychiatric emergency to manage, especially among vulnerable categories such as patients with Intellectual Developmental Disorder. Although there is some evidence that clozapine may be useful as an anti-violence compound, its use is limited by common metabolic complications. An adult patient presented with obesity, type II diabetes mellitus, compulsive food intake, severe Intellectual Developmental Disorder, and a treatment-resistant aggressive behaviour. Clozapine was administered resulting in reduced aggressive behaviour. Unexpectedly, a reduction in the food craving as well as a sustained improvement in both anthropometric parameters and glycemic control were observed during the clozapine treatment. Our case report, describes these findings for the first time, highlighting the need for more clinical research to investigate both the efficacy of clozapine in the Intellectual Developmental Disorder populations and its long-term effects with special regard to the metabolic outcomes in this type of patients.