The most common method for determining if a patient is a good candidate for weight loss surgery is by following the National Institute of Health guidelines.  These guidelines typically state that a patient should have a Body Mass Index (BMI) of over 40 or have a BMI of over 35 with a co-morbid condition such as type 2 diabetes, sleep apnea, hypertension, etc.  Some patients with a BMI between 30 and 35 may be candidates for surgery if other medical conditions indicate that surgery would be beneficial for the patient.  In all cases, you should be prepared to discuss your health history with your surgeon to determine if you are a weight loss surgery candidate and if so, which surgery might be best for you.