Jeff W. Allen, M.D., director, bariatric surgery, Norton Weight Management Services; general, bariatric and laparoscopic surgeon, Norton Surgical Specialists

Only 2% to 5% of morbidly obese patients eligible for weight loss surgery act on it, despite the lifesaving possibilities. It’s a very personal decision. Unfortunately, most people identified as morbidly obese decide to do nothing.

People qualify for weight loss surgery based on their body mass index (BMI). Anyone with a BMI of 40 or above and a history of trying to lose weight automatically qualifies. Having a BMI between 30 and 40 along with a disease related to obesity, such as diabetes, also qualifies.

The three most common surgical interventions are gastric bypass, sleeve gastrectomy and gastric band. Of the three, sleeve gastrectomy is the most common. All of them can be performed laparoscopically. There isn’t one that’s clearly superior, so a lot of the choice depends on patient preference. Each of the operations has pros and cons.

Gastric bypass creates a small pouch at the top of the stomach about the size of an egg, limiting how much someone can comfortably eat and drink at one time. The pouch is connected to a lower section of the small intestine. This bypass means the body will absorb fewer calories. With gastric bypass, weight loss typically happens quickly and is lasting.

Because nutrients are not absorbed as they were previously, gastric bypass carries a risk of anemia and osteoporosis. Another risk is dumping syndrome, which occurs when food dumps from the stomach to the small intestine too quickly, resulting in symptoms such as nausea, bloating, pain, sweating, weakness and diarrhea.

Sleeve gastrectomy removes about 80% of the stomach, leaving a sleeve-like tubular pouch that connects to the small intestine. Risks include leaking, infection and blood clots.

Gastric band uses an inflatable band to squeeze the stomach and divide it in two, with only a small channel connecting a smaller upper pouch and a larger lower pouch. This small channel slows the emptying of food from the upper pouch. The result is that the person feels full after eating 1 cup or less of food.

The gastric band procedure has the lowest complication rate, but it also results in the slowest weight loss. In addition, patients need to come back frequently for adjustments to the band, which controls how much food flows from one part of the stomach to the other. The band is tightened or loosened by adding or removing saline.

All of these weight loss surgeries are highly effective. The average person will lose 70% of excess body weight within two years after surgery. However, patients have to want to undergo the procedure or it is likely to fail. I’ve had patients lose more than 500 pounds.

I’ve had other patients lose nothing. After surgery, I hand the torch to them. It’s up to them to do the work.