Ten years after gastric-bypass weight-loss surgery, patients in a recent study had managed to keep off much of the weight they'd lost.

Even more important, they also saw reductions in other medical problems, such as diabetes, high blood pressure, high cholesterol, joint diseases and problems breathing while asleep, said Dr. J. Hunter Mehaffey.

Mehaffey, from the University of Virginia School of Medicine, told Reuters Health by phone, "It's not just that people are losing a lot of weight, but they're also much healthier."

In gastric bypass operations, surgeons remove part of the stomach and reroute the intestines to help patients with extreme obesity lose weight.

The American Society of Metabolic and Bariatric Surgery estimates that in 2014, 193,000 people in the U.S. underwent weight loss operations, known collectively as bariatric surgery. The different procedures include gastric bypass, adjustable gastric banding and sleeve gastrectomy.

Using a large database, Mehaffey and colleagues identified 1,087 patients who had gastric bypass surgery for morbid obesity between 1985 and 2004.

Ten years later, the authors were able to contact 651 of the patients by phone.

Most were white and female, in their early 40s, on average. At the time of the surgery, their average body mass index - a ratio of weight to height - was in the low to mid 50s. A normal body mass index (BMI) ranges from 18.5 to 24.9.

(You can calculate yours here, courtesy of the National Institutes of Health: http://1.usa.gov/1ooHYzU.)

By two years after the operation, patients had lost 74 percent of their excess BMI, on average. At 10 years, they had still kept off more than half of the excess BMI that they had lost, and more than 25 percent of their original total body weight loss.

When they had their surgery, 41 percent of the patients had diabetes, 25 percent had heart disease, 59 percent had high blood pressure and 36 percent had sleep apnea, the authors reported in Annals of Surgery.

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At the 10-year point, only 18 percent still had diabetes, 16 percent had heart disease, 47 percent had high blood pressure, and 16 percent had sleep apnea.

The rate of joint disease had dropped from 61 percent to 32 percent. And the rate of reflux disease had fallen from 38 percent to 29 percent.

"The benefits are immense," said Dr. Amir Ghaferi, a bariatric surgeon at the University of Michigan Health System who was not part of the study. "There's proven evidence that this type of surgery has benefits that exceed intensive medical management like counseling, dietary assistance and exercise programs."

But Ghaferi emphasized that the study didn't represent all the surgery options currently available.

"Gastric bypass is considered the gold standard, but over the past five or six years, there have been more sleeve gastrectomy procedures," he said.

Still, Ghaferi said, the new findings are useful.

"There's always a concern about weight regain over time so it's good to see 50 percent of excess (BMI) was kept off at 10 years," he said.

But he cautioned that weight loss surgery is a tool, not a solution.

"It's a piece of the puzzle on how to treat and manage obesity, but you can slip back into your bad habits," he said. "That's why surgery follow up is vital to treatment success."