Adults with a body mass index (BMI) between 25 and 29.9 kg/m² are considered overweight. Those with a BMI ≥30 are considered obese. Losing even a small amount of weight and increasing physical activity can prevent some of the complications of obesity, particularly type 2 diabetes. Diet and exercise are the preferred methods for losing weight, but long-term failure rates are high. Several drugs have been approved by the FDA for weight reduction, but adherence is poor, adverse effects are common, and patients usually regain the lost weight when the drug is stopped. Bariatric surgery can produce substantial weight loss and significantly reduce obesity-related comorbidities; long-term data on its safety are encouraging, but still limited. Guidelines for the management of overweight or obese adults have recently been published.

The FDA has approved a fixed-dose combination of the opioid receptor antagonist naltrexone (ReVia, and others) and the antidepressant and smoking cessation agent bupropion (Wellbutrin SR, Zyban, and others), as Contrave (Orexigen/Takeda) for weight loss. The combination was approved for use as an adjunct to diet and increased physical activity in patients with a body mass index (BMI) ≥30 kg/m² or a BMI ≥27 kg/m² and one or more weight-related comorbidities such as hypertension, diabetes, or dyslipidemia. Naltrexone/bupropion is not a controlled substance.

In 2013 the FDA approved one new drug and a new combination of 2 old drugs as adjuncts to lifestyle changes for chronic weight management. Lorcaserin (lor-ca-SER-in; Belviq – Arena/Esai) is a selective serotonin 2C receptor agonist. Qsymia (Vivus) is a fixed-dose combination of the weight-loss drug phentermine and an extended-release (ER) formulation of topiramate. The new products are approved for use in obese patients (body mass index [BMI] of ≥30 kg/m²) and for patients who are overweight (BMI ≥27 kg/m²) and have one weight-related risk factor such as hypertension, dyslipidemia or type 2 diabetes.