Overnutrition and sedentary lifestyle result in overweight or obesity defined as abnormal or excessive fat accumulation that may impair health. According to the WHO, the worldwide prevalence of obesity nearly doubled between 1980 and 2008. In 2008, over 50% of both men and women in the WHO European Region were overweight, and approximately 23% of women and 20% of men were obese. Comprehensive diagnostic and therapeutic approaches should include nutritional treatment to favor the best metabolic and nutritional outcome, as well as to induce potential disease-specific benefits from selected nutritional regimens. Obesity is usually accompanied by an increased muscle mass. This might explain why obesity, under particular circumstances such as cancer or high age, might have protective effects, a phenomenon named the 'obesity paradox'. However, loss of muscle mass or function can also occur, which is associated with poor prognosis and termed 'sarcopenic obesity'. Therefore, treatment recommendations may need to be individualized and adapted to co-morbidities. Since obesity is a chronic systemic disease it requires a multidisciplinary approach, both at the level of prevention and therapy including weight loss and maintenance. In the present personal review and position paper, authors from different disciplines including endocrinology, gastroenterology, nephrology, pediatrics, surgery, geriatrics, intensive care medicine, psychology and psychiatry, sports medicine and rheumatology, both at the basic science and clinical level, present their view on the topic and underline the necessity to provide a multidisciplinary approach, to address this epidemic.