On average, patients undergoing gastric bypass surgery can expect to lose about 60% of their excess weight after bypass surgery. This means that if you are about 150 pounds overweight, you can expect to lose about 90 pounds.

Statistics vary but about 5-20% of patients will regain weight despite having gastric bypass surgery. This indicates that we still don’t fully understand the psychopathology of binge eating and its impact on gastric bypass surgery as one 2002 study of binge eating in gastric bypass patients concluded.

The two most common types of weight loss surgery are laparoscopic gastric banding and gastric bypass surgery with weight loss expected to be between 45-75% and 50-75% respectively. Gastric bypass surgery should be done by an experienced surgeon.

For more information about these types of surgery, UpToDate has an excellent patient handout on weight loss surgical options.