Why Weight-Loss Surgery Mysteriously Reverses Diabetes in Some Patients

Diabetic patients who undergo weight-loss surgery often see their diabetes suddenly disappear, before they've even lost much weight. Now researchers are coming closer to finding out the reason for this remarkable phenomenon.

Weight-loss surgery and dieting alter the body's metabolism in different ways, the researchers say. The changes produced after weight-loss surgery may be particularly beneficial for reversing diabetes .

About 50 to 80 percent of patients who have gastric bypass surgery (a type of weight-loss surgery) see a reduction in their blood glucose levels that's enough for them to be considered free of the disease. Sometimes, this can happen within hours after surgery, said study researcher Dr. Blandine Laferrère, of St. Luke's and Roosevelt Hospital Center in New York City. Such remission is rarely seen after dieting alone, the researchers say.The results show patients who received gastric bypass surgery have reduced levels of certain amino acids in their blood compared with those who achieve weight loss through diet alone. Amino acids are the building blocks of proteins in the body.

Much more research is needed to determine how this decrease in amino acids and other changes in metabolism might contribute to diabetes remission. But future investigations may yield new ways to treat diabetes -- doctors may be able to mimic the effects of weight-loss surgery without requiring patients to go under the knife.

Researchers want to "understand better what causes Type 2 diabetes with the hope of developing some new treatment models" for the condition, Laferrère said.

However, experts point out the surgery is not without risks. It can cause malabsorption of nutrients. Indeed, the reason for the decrease in blood amino acid levels in the patients after surgery may be malabsorption of protein, said Dr. Sunil Bhoyrul, a bariatric surgeon at Scripps Memorial Hospital in La Jolla, Calif.

"It really shows the double-edge sword of malabsorption," Bhoyrul said. "It might be a good explanation for why you get a better resolution of diabetes. But it also may be the cause of protein malabsorption," Bhoyrul said. Because of this issue, use of the surgery should be approached with caution, he said.

The study was published today (April 27) in the journal Science Translational Medicine.

'Diabetes surgery'

Type 2 diabetes occurs when the body does not properly respond to insulin. This hormone is needed to get sugar, or glucose, into cells. By the time diabetes develops, the cells are resistant to insulin, and sugar builds up in the bloodstream. Patients with diabetes are at an increased risk for heart disease, stroke, kidney failure and blindness, according to the National Institutes of Health.

Researchers have hypothesized that changes in gut hormones may contribute to diabetes reversal after surgery, but other factors might also play a role.

Laferrère and colleagues at Duke University Medical Center in Durham, N.C., studied two groups of obese individuals with a body mass index, or BMI, over 35 (BMI is a ratio of height and weight and is considered an indicator of body fatness.) One group of 10 participants underwent gastric bypass surgery and were followed up one month after their surgery. The other, with 11 subjects, went on a diet to achieve about a 20-pound (10 kilogram) weight loss .

Both groups lost about the same amount of weight (20 pounds), but those who received the surgery saw a significant decrease in their blood glucose levels.

They also had much lower levels of amino acids called branched-chain amino acids compared with those who lost the weight through dieting. These types of amino acids have been associated with insulin-resistance and heart disease.

Higher levels of amino acids in the blood may prevent insulin from working normally, Laferrère said.

The researchers now want to find out how changes in amino acid levels relate to changes in gut hormones after surgery.

Selecting patients

It's possible the differences in amino acid levels might be because those on the diet ate more protein than those who underwent surgery. But all patients had their blood samples after fasting for a night, making it less likely the subjects' diet influenced their blood amino acid levels. This also means differences in amino acid levels might not be due to malabsorption, Laferrère said.

But malabsorption is still a risk. The surgery causes food to bypass a section of the gut in which certain nutrients may be absorbed, Bhoyrul said Bhoyrul says studies like these can help doctors decide who will benefit most from gastric bypass surgery.

Someone with newly diagnosed diabetes might be better off receiving gastric banding, which restricts the stomach but doesn't come with as high a risk of malabsorption.

But for a patient with longstanding severe diabetes, the risks of malabsorption from gastric bypass might be outweighed by the reversal of diabetes from the surgery, Bhoyrul said.

"This kind of study may help us choose the right operation for the right patient," Bhoyrul said.

Pass it on: Gastric bypass surgery may cause reductions in the blood levels of certain amino acids, which in turn may contribute to diabetes remission.

Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner.

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.