What is the problem and what is known about it so far?

About one-third of the people in the United States are obese. The rise in the rate of obesity is linked to more people getting type 2 diabetes, high cholesterol, high blood pressure, and heart disease.

Unfortunately, many obese people have a hard time losing weight with dieting and exercise alone.

In 1991, the National Institutes of Health wrote guidelines for weight-loss surgery for people who are morbidly obese (people who will die if they don't lose weight). Someone who is morbidly obese has an extremely high body mass index (BMI, a measure of weight in proportion to height) and often has other diseases, too.

Why did the researchers do this particular study?

The researchers wanted to collect as much information as possible about weight-loss surgery (also called "bariatric surgery"). They wanted to know if weight-loss surgery helps people with diabetes, high cholesterol, high blood pressure, and sleep apnea (a condition that makes it difficult to breathe while a person sleeps).

Who was studied?

This study reviewed 136 weight-loss surgery studies done between 1990 and 2003. Each study included at least 10 patients who had weight-loss surgery and reported outcomes on at least one of the four diseases stated above.

A total of 22,094 patients were included, from ages 16 to 64. Nineteen percent were men, 73% were women, and the sex of 8% was not reported.

How was the study done?

The researchers studied results of weight-loss surgeries for each of the four types of diseases for the total population. They collected information about weight loss and BMI before and after surgery and also grouped outcomes for the four selected diseases into two categories. Those in the "resolved" group had conditions that disappeared or no longer needed treatment.

What did the researchers find?

Morbidly obese people who had weight-loss surgery lost between 47.5% and 70.1% of their excess weight, depending on the type of weight-loss surgery they had. Thirty days after the surgery, the rate of death ranged from 0.1% to 1.1%, depending on the type of weight-loss surgery.

Weight-loss surgery helps reduce the seriousness of all four of the diseases studied. Diabetes completely disappeared in 76.8% of the patients and was resolved or improved in 86%. High cholesterol improved in 70% of the patients. High blood pressure disappeared in 61.7% of patients and was resolved or improved in 78.5%. Obstructive sleep apnea, or breathing disturbances during sleep, disappeared in 85.7% of patients and was resolved or improved in 83.6% of patients.

What were the limitations of the study?

Long-term health outcomes are not included for many of the patients included in these studies.

What are the implications of the study?

In addition to losing a lot of weight, most morbidly obese people who choose to have weight-loss surgery have better health since the diseases related to their weight disappear or improve. Although there are some risks and inconveniences with weight-loss surgery, the researchers suggest that a person's quality of life should improve after someone has weight-loss surgery.

- American Diabetes Association