Surgery can help reduce obesity-related problems

Q: How can I tell if weight-loss surgery would be right for me?

A: Surgery to promote weight loss (called bariatric surgery) is appropriate for two groups of people. The first group includes people who have severe obesity, which is roughly equivalent to being 80 pounds overweight for a woman or 100 pounds for a man. Severe obesity, which affects about 5 percent of Americans, is officially defined as having a body mass index (BMI) of 40 or more. (To calculate your BMI, which is a measure of body fat based on height and weight, divide your weight in pounds by your height in inches squared and multiply by 703. You can also use the online calculator at http://nhlbisupport.com/bmi/) The second group includes people who have BMIs between 35 and 40 and also have an obesity-related health problem, such as type 2 diabetes, heart disease or sleep apnea.

Research has shown that diet and weight-loss medications are of little use to people with extreme obesity. Bariatric surgery is their best chance for long-term weight reduction and improved health. Even more than a decade after surgery, 90 percent of those who have undergone gastric bypass, the most common procedure, manage to keep off an average of 50 percent of the excess weight. The result is a cure or improvement of the many health problems linked to obesity mentioned above. Weight loss also lowers the risk of many other problems linked to excess weight, including arthritis, high blood pressure, stroke and certain cancers.

Surgeons have been doing bariatric surgery for more than 50 years. But the number of people undergoing the procedure (most of whom are women) has soared - from 36,700 in 2000 to 171,000 in 2005, according to figures from the American Society for Bariatric Surgery. A growing number of extremely obese people have fueled this surge. So have better surgical techniques and high-profile success stories, such as NBC TV weatherman Al Roker's loss of 100 pounds after gastric bypass in 2002.

Like all major operations, bariatric surgery has risks. Surgical treatment also requires lifelong medical monitoring and major changes in diet and lifestyle. But for most people with extreme obesity, the health benefits far outweigh the risks.

People often assume that bariatric surgery works because it forces people to eat less. But it's actually more complex. Some procedures, such as gastric banding, restrict food intake by making the stomach smaller. Roux-en-Y gastric bypass restricts food intake and also changes the absorption of some fats and other nutrients. But hormonal changes also play a role. For example, levels of ghrelin, a hormone that stimulates appetite, decrease after gastric bypass. Surgery may also affect the body's production and response to insulin, a hormone that affects blood sugar levels.

If you think surgery might be right for you, ask your primary care provider to refer you to a bariatric surgeon or a center that specializes in bariatric procedures. First, clinicians specializing in medicine, nutrition and psychology will evaluate you. The purpose is to make sure you are physically and mentally prepared for surgery and the accompanying changes. You must also be willing and able to participate in follow-up care and diet, and understand all the potential risks and benefits.

For the first few months after surgery, you'll be allowed to eat only several hundred calories per day. Don't worry - you won't feel starved, because you'll have little appetite or interest in food. If you eat too quickly or too much, the stomach pouch will overfill and you may vomit or feel pain in the chest and upper abdomen. You'll need to take supplementary vitamins (especially vitamins B-1, B-12, folate and D) and minerals (especially calcium and iron). After about a year, most people can increase their intake to 1,200 calories per day.

You may be advised to take a medication to prevent gallstones, which develop in 30 percent of people who lose weight rapidly. Kidney stones are also common. Ulcers may occur in the small intestine because of contact with stomach acid. Some people develop other complications, such as a hernia at the incision site.

After a high-carbohydrate meal, a person who has had gastric bypass surgery may suffer from "dumping syndrome." This causes flushing, sweating, nausea, vomiting and sometimes diarrhea. Gas is another common complaint. People who lose 100 pounds or more sometimes need additional surgery to "lift" sagging skin that won't return to normal.

Insurance coverage for bariatric surgery varies. In February, Medicare announced that it will cover certain bariatric procedures for people treated at centers endorsed by the American College of Surgeons or the American Society for Bariatric Surgery.

Harvard Medical School faculty members write this column. To submit questions, e-mail harvard_adviser@hms.harvard.edu .