Obesity, a widespread and growing problem in industrialized countries, engenders many medical, psychosocial and economic issues. In 1990s, the body mass index (BMI) became a universally accepted measure of the degree of overweight and now identical cutoff points are recommended. In the Western countries, cutoff points of 25 and 30 kg/m2 are used for describing overweight and obesity. However, in Asian countries, the absolute health risk (particularly of type 2 diabetes mellitus) seems to be higher at the same level of BMI. The international obesity task force (IOTF) suggested the cutoff points to be 23 kg/m2 for overweight and 25 kg/m2 for obesity in Asian countries. Consensus for obesity treatment is that clinical therapy should begin with lifestyle changes focusing on behavioral modification, diet, and exercise. When lifestyle modification schemes are unsuccessful, drug therapy is an attractive option. The use of anti-obesity drug has become increasingly common in the last 30 years. In conclusion, the prevalence of obesity is increasing at an alarming rate in many parts of the world. Thus, increased attention should be paid to people who are at high risks. Anti-obesity drugs may be an option for weight control; however, they should be used under regulation and with caution.