Bacteria that live in the gut change after gastric-bypass surgery and may aid in weight loss, a Harvard University study shows.

Mice got the stomach-shrinking surgery and changes in the gut's bacterial inhabitants were monitored in the study, reported in the journal Science Translational Medicine. When bacteria from mice that got surgery were transferred into mice with no gut germs, those mice also lost weight, about a fifth what they would have lost with surgery.

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Gastric surgery helps people lose weight by shrinking the size of the stomach, making it tougher to absorb calories. Now scientists think it may also adjust gastrointestinal bacteria, leading to weight loss and raising the possibility for less-drastic obesity treatments, the authors say.

"A major gap in our knowledge is the underlying mechanism linking microbes to weight loss," said Peter Turnbaugh, a systems biologist at Harvard. -- Bloomberg News