Los Angeles ? The first long-term studies of stomach stapling and other radical obesity treatments show that they not only lead to lasting weight loss but also dramatically improve survival. The results are expected to lead to more such operations, possibly for less severely obese people, too.

Researchers in Sweden and the United States separately found that obese people who underwent drastic surgery had a 30 percent to 40 percent lower risk of dying seven to 10 years later compared with those who did not have such operations.

The research should put to rest uncertainties about the benefits and risks of weight-loss surgery and may cause governments and insurers to rethink who should qualify for the procedure, some doctors said.

“It’s going to dispel the notion that bariatric surgery is cosmetic surgery and support the notion that it saves lives,” said Dr. Philip Schauer, director of bariatric surgery at the Cleveland Clinic in Ohio, who had no role in the research.

Obesity surgeries have surged in recent years along with global waistlines.

In the United States alone, 177,600 operations were performed last year, according to the American Society for Metabolic & Bariatric Surgery. The most common method was gastric bypass, or stomach-stapling surgery, which reduces the stomach to a small walnut-sized pouch and bypasses part of the small intestine where digestion occurs.

The Swedish study is the longest look yet at how obesity surgery affects mortality.

Researchers compared 4,047 people with a body-mass index over 34 who had one of three types of surgery or received standard diet advice. BMI is a standard measure of height and weight and a BMI over 30 is considered obese.

Deaths from diabetes in the surgery group were dramatically cut by 92 percent; from cancer by 60 percent and from heart disease by 56 percent.

Surprisingly, the surgery group had a higher risk of death from accidents, suicides and other causes not related to disease. The researchers were puzzled by this.