(CNN) — A once-a-week injected diabetes drug helped overweight and obese people lose an average of 15% of their body weight over 16 months, researchers reported Wednesday.

The maker of the drug, called semaglutide, has asked the US Food and Drug Administration to approve it for chronic weight management. If approved, it would be only the fifth prescription weight loss drug on the US market.

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Semaglutide is a glucagon-like peptide-1 receptor, or GLP-1 agonist — a drug that increases the production of insulin. But it also appears to suppress appetite.

“Weight loss with semaglutide stems from a reduction in energy intake owing to a decreased appetite, which is thought to result from direct and indirect effects on the brain,” Dr. Robert Kushner of Northwestern University and colleagues across the country wrote in their report, published in The New England Journal of Medicine.

They tested it in 1,961 people who were either overweight or obese. A third got placebo plus dietary counseling and exercise coaching, while two-thirds got the drug with the same diet and exercise plan.

“The mean change in body weight from baseline to week 68 was 14.9% in the semaglutide group compared with 2.4% with placebo,” Kushner’s team wrote. On average, people who took the drug lost 15.3 kg, or 33 pounds.

People who took the drug were more likely to suffer nausea, diarrhea, vomiting or constipation, the researchers said. Nearly three-quarters did, compared to just under half of those who took placebo.

But 80% of the volunteers stuck it out for the trial that lasted nearly a year and a half. The researchers think at least some people would accept a once-a-week injected drug.

“Currently, approved antiobesity drugs require administration once, twice or three times daily, and a once-weekly regimen may improve treatment adherence,” they wrote.

According to the US Centers for Disease Control and Prevention, 42% of Americans are obese, meaning they have a body mass index of 30 or more. Obesity raises the risk of heart disease, cancer, stroke and diabetes.

But there are few good treatments.

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Dr. Julie Ingelfinger and Dr. Clifford Rosen of Tufts University, who were not involved in the study, called the study a “good beginning.”

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“The results are encouraging,” they wrote. But they saw big weaknesses. “First, the demographics in this trial are not reflective of the general US population. Most of the participants were White, with only 6% Black or African American and 12% Latinx, whereas nearly 40% of the US population is non-White,” they wrote in a commentary in The New England Journal of Medicine.

It also did not look at long-term efficacy. “In sum, we have a long way to go to control the obesity epidemic,” they wrote.

Other outside researchers had no quarrel with the study, but noted that weight loss drugs have not performed well in real life. Many have been pulled from the market because of side effects.

“While a drug like this may prove useful in the short term for obtaining rapid weight loss in severe obesity, they are not a magic bullet for preventing or treating less severe degrees of obesity,” Tom Sanders, professor emeritus of nutrition at King’s College London, said in a statement.

“Public health measures that encourage behavioral changes such as regular physical activity and moderating dietary energy intake are still needed. It is rather like the situation we are in with the (coronavirus) vaccine — we still need to stick with public health measures and not become overdependent on medicines.”

Few drugs are approved in the US specifically for weight loss. They include orlistat, sold under the brand name Xenical, which helps reduce the amount of fat the body absorbs; Qsymia, a drug that combines the appetite reducer phentermine with the seizure drug topiramate; Contrave, which combines the addiction drug naltrexone with the antidepressant bupropion; and liraglutide or Saxenda, a diabetes drug that is similar to semaglutide.

In general, these drugs have been shown to help people lose 3% to 7% of body weight.

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