Many people who suffer from obesity find it difficult to lose weight and keep it off with diet and exercise alone. This is probably due to nutrition and health related characteristics.

The National Institutes of Health (NIH) Expert Panel stated that without surgery, long-term weight loss is nearly impossible for those with severe obesity. Studies show little long-term success with diet and exercise alone. When a person goes on a diet, their body produces more hormones that cause an increase in hunger and a decrease in calories burned. There are significant differences between someone who has lost weight by dieting and someone of the same size who has never lost weight. For example, the body of the person who reduces his or her weight from 200 to 170 pounds burns fewer calories than the body of a 170-pounder who has never been on a diet. Weight loss procedures cause biological changes that help reduce food intake. Energy intake (in the form of food) decreases with surgery by restricting stomach size and limiting absorption. In addition, surgery modifies the production of certain intestinal hormones (or signals) that communicate with the brain to reduce hunger, decrease appetite and increase satiety. In this way, weight loss surgery, unlike dieting, produces long-term weight loss.