Obesity is among the leading causes of morbidity and mortality worldwide and its prevalence continues to increase globally. Because obesity is a chronic, complex, and heterogeneous disease influenced by genetic, developmental, biological, and environmental factors, it is necessary to approach obesity with an integrated and comprehensive treatment strategy. As it is difficult to achieve and sustain successful long-term weight loss in most patients with obesity through lifestyle modifications (e.g., diet, exercise, and behavioral therapy), pharmacological approaches to the treatment of obesity should be considered as an adjunct therapy. Currently, four drugs (orlistat, naltrexone extended-release [ER]/bupropion ER, phentermine/topiramate controlled-release, and liraglutide) can be used long-term (>12 weeks) to promote weight loss by suppressing appetite or decreasing fat absorption. Pharmacotherapy for obesity should be conducted according to a proper assessment of the clinical evidence and customized to individual patients considering the characteristics of each drug and comorbidities associated with obesity. In this review, we discuss the mechanisms of action, efficacy, and safety of these available long-term anti-obesity drugs and introduce other potential agents under investigation. Furthermore, we discuss the need for research on personalized obesity medicine.