Researchers found levels of branched amino acids showed significantly greater reductions after surgery than after diet-induced weight loss.
They said the finding 'suggests a role for alterations in circulating amino acids in mediating enhanced glycaemic control in gastric bypass surgery compared with diet-induced weight loss'.
Dr Blandine Laferrere and colleagues from St Luke's Roosevelt Hospital Centre, New York, studied 15 patients who underwent gastric surgery and 17 patients who dieted to achieve equivalent weight loss.
Diabetes remission occurs after up to 80% of gastric surgery, but is rarely seen after equivalent weight loss achieved by dieting, the researchers said.
The researchers measured more than 20 parameters before and after weight loss to see if changes in these might explain the remission in diabetes.
They found that levels of the branched-chain amino acids leucine, isoleucine and valine and related metabolites fell more in the surgery group than the diet group.
Concentrations of branched-chain amino acids have been linked to insulin resistance, the researchers said.
The researchers said: 'These data suggest that the enhanced decrease in circulating amino acids after gastric bypass surgery occurs by mechanism other than weight loss and may contribute to the better improvement in glucose homeostasis observed with the surgical intervention.'