Weight-loss surgery is only recommended if you cannot lose a large amount of weight and keep it off by dieting, changing your behavior, and exercising alone. Doctors often use the body mass index (BMI) and health conditions such as type 2 diabetes and high blood pressure to determine which patients are most likely to benefit from weight-loss surgery. Patients who qualify are those with a BMI above 32.5 kg/m2, with associated co-morbidities like diabetes, etc, or patients with BMI above 37.5 kg/m2, with or without associated co-morbidities.