Weight-loss surgery is a specific type of operation to help severely obese people who have 100 pounds or more to lose in their quest to both lose weight and keep it off permanently. It alters the anatomy of your digestive system, physically limiting the amount of food that your body can consume as well as absorb. It does this in one of two ways: making the stomach smaller (restriction), or preventing calories from being absorbed into the body (malabsorption).

While there are different surgical options, the most important thing to remember is that weight-loss surgery supports an effort to change your lifestyle. That’s the true foundation of successful weight loss. Anyone considering weight-loss surgery needs to embrace a healthy lifestyle before and after the operation, since surgery does not replace the lifestyle effort. It only supports it.

Weight-loss surgery is performed primarily to cause someone to eat less or absorb fewer calories. Eating less is achieved by reducing the size of the stomach. Absorbing fewer calories happens when parts of the stomach and intestines are bypassed, so they’re not exposed to the food and calories as they go through the digestive tract. Current surgeries may also work by causing changes in the chemicals and hormones that the body makes, thereby decreasing appetite.

There are different kinds of surgery. Gastric bypass surgery (Roux-en-Y) works to both decrease the stomach size and to bypass part of the stomach and small intestine. Gastric banding surgery (Lap-Band, Realize) acts primarily by decreasing the size of the upper stomach and allowing fullness with much less food intake. Other surgeries, such as the “sleeve” procedure, are also available. If you’re considering surgery, it’s important to fully research which ones are available, how long they have been performed and what the long-term data shows about their success.

Weight-loss surgery (aka bariatric surgery) consists of a group of surgical operations designed to achieve both meaningful and sustainable weight loss. These procedures involve surgically manipulating the stomach (and sometimes the small intestines) to reduce food intake, and, in some cases, to reduce the absorption of calories into the body. The procedures include:

• Adjustable gastric banding: This common surgery achieves weight loss solely by restricting how much food one can eat.
  
  
• Gastric bypass: This common surgery achieves weight loss not only by restricting how much food one can eat, but also through hormonal changes, appetite reduction, food intolerances and mild malabsorption, in which the body absorbs fewer calories and nutrients.
  
  
• Biliopancreatic diversion: A less commonly performed operation, in which the intestines are bypassed, this achieves weight loss predominantly by limiting the absorption of calories consumed.
  
  
• Vertical sleeve gastrectomy: Also less common, this procedure involves removing part of the stomach. It is a new procedure and the exact mechanism of action has not yet been determined.
  

Currently, all of these procedures can be and are performed laparoscopically, meaning that surgeons operate through several small incisions with the aid of a video camera rather than through a long incision. This means less risk of complications, quicker healing, and less scarring.

About a decade ago, I was on the National Institutes of Health panel that wrote the clinical guidelines on the identification, evaluation and treatment of overweight and obesity in adults. We agreed that:

• Diet and exercise should be the first interventions for losing weight, because they are the least intrusive and have few negative side effects.
  
  
• If those strategies were not effective, weight-loss drugs should come next.
  
  
• If drugs were not helpful, then surgery might be considered.
  

The main problem that we found: Weight losses achieved through diet, exercise and drugs generally were quite modest, around 10 to 20 pounds on average, and regaining the lost weight was common. Often, these strategies were especially ineffective for people needing to lose a lot of weight. On the other hand, surgical interventions for weight loss generally produced large weight losses, often 100 pounds or more over one year, with less initial regain.

A decade later, the results are even more pronounced. Weight-loss surgery is an effective intervention to limit caloric intake and subsequently to lose large amounts of weight. For severely obese adults who have struggled unsuccessfully in their weight-loss attempts, bariatric surgery today is an acceptable and effective approach for losing clinically significant amounts of weight.