The researchers compared 11 gastric bypass surgery patients who had diabetes with 11 others who had diabetes and achieved equivalent weight loss with diet alone.

The average age of patients in the diet group was about 55, while the average in the surgery group was 49. Those in the surgery group lost an average of 51 pounds, while those in the diet group lost an average of 48 pounds, reports Xinhua.

Over a 24-hour period, the researchers used sophisticated techniques in a hospital setting to measure study subjects' metabolic responses to meals.

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They found the members of both groups experienced similar improvements in metabolism, such as lower blood sugar levels throughout the day, better insulin action in the liver, muscle and fat tissue, and reductions in the need for insulin and other diabetes medications.

"It has been suggested that weight loss induced by gastric bypass surgery is different from weight loss induced by a low-calorie diet, based on the fact that certain factors, such as increased bile acid concentrations, decreased branched-chain amino acid concentrations and alterations in the gut microbiome, are different in surgery patients and may be responsible for the unique therapeutic effects of gastric bypass surgery," said principal investigator Samuel Klein, director of Washington University's Center for Human Nutrition.

 "We found all of those factors were, in fact, different after weight loss in surgery patients than in patients who lost weight through diet alone. Yet those changes were not associated with any physiologically or clinically important metabolic benefits,” said the Samuel Klein.

The loss of weight is the reason for improvements in metabolic function and reversal of diabetes. Weight loss through dieting produces the same beneficial metabolic effects as weight loss following surgery, said Klein.

More than 40 percent of adult Americans are obese, and close to one in 10 is severely obese. Each year more than 250,000 people in the United States undergo bariatric surgery to help them lose weight.

The study was published Thursday in The New England Journal of Medicine.