Decreasing levels of patient motivation or compliance are far from being the only causes of postinterventional weight regain after lifestyle, psychological, pharmacological and surgical interventions. Weight regain originates from acomplex and individually varying set of central and peripheral mechanisms, with the overall purpose of increasing food intake by both stimulating hunger and reducing satiety (mediated by gastrointestinal hormones) and decreasing the body's energy demands (via metabolic adaption). These mechanisms counteract any attempts to reduce or maintain body weight in today's increasingly prevalent adipogenic environments. The knowledge about the biological mechanisms of body weight regulation should be taken into consideration when planning treatment programs for long-term weight reduction, including follow-up treatment for the prevention and individualized treatment of postinterventional weight regain. Therapeutic measures as well as the frequency of medical follow-ups should be based on the extent of weight regain.