Obesity is related to increased morbidity and mortality, and prevails worldwide. It has become an important health issue and requires urgent attention. In Taiwan, overweight and obesity are defined as body mass index ≥24 and 27 kg m−2, respectively. These cut-offs differ from Caucasian standards, as Asians have higher comorbidities and fat mass at lower BMI levels than Caucasians. The prevalence of obesity and overweight in Taiwan are 19.2% and 30.5% in men, 13.4% and 21.3% in women. This implies that a more profound increase in obesity prevalence is found in men than in women. A high-fat diet, sedentary lifestyle and betel nut chewing may increase substantially this obesity epidemic. Recently, type 2 diabetes mellitus has been found to be the most common type of diabetes, and obesity is significantly related to type 2 diabetes in children. In addition, obesity is associated with cardiovascular diseases risk factors and cannot be neglected in elderly. Therefore, a comprehensive prevention and management programme of obesity is urgently warranted for controlling the growing obesity trend and its related diseases in Taiwan.