Bariatric surgery is currently the most effective method of sustainable weight loss among morbidly obese patients. The types of bariatric surgeries can be divided into three categories: restrictive procedures, malabsorptive procedures, and combination (restrictive and malabsorption) procedures. In general, patients undergoing restrictive procedures have the least risk for long-term diet-related complications, whereas patients undergoing malabsorptive procedures have the highest risk. For many patients, the benefits of weight loss, such as decreased blood glucose, lipids, and blood pressure and increased mobility, will outweigh the risks of surgical complications. Most diet-related surgical complications can be prevented by adhering to strict eating behavior guidelines and supplement prescriptions. Eating behavior guidelines include restricting portion sizes, chewing foods slowly and completely, eating and drinking separately, and avoiding foods that are poorly tolerated. Supplement prescriptions vary among practitioners and usually involve at least a multivitamin with minerals. Some practitioners may add other supplements only as needed for diagnosed deficiencies; others may prescribe additional prophylactic supplements. The most common nutrient deficiencies are of iron, folate, and vitamin B12. However, deficiencies of fat-soluble vitamins have been reported in patients with malabsorption procedures, and thiamin deficiency has been reported among patients with very poor intake and/or nausea and vomiting. Frequent monitoring of nutrition status for all patients can aid in preventing severe clinical deficiencies.