Taking the right mix of bacteria could lead to a form of "knifeless gastric bypass," a surgery-free method of causing the kind of significant weight loss associated with procedures that reduce the size of the stomach. According to New Scientist magazine, researchers at Massachusetts General Hospital in Boston have been able to induce weight loss in normal mice by introducing gut bacteria from mice who had undergone gastric bypass. The findings could lead to a similar treatment program for human obesity.

Gastric bypass surgeries have proven to be a highly successful method of treating obesity and associated diseases like type 2 diabetes. Patients who have the procedure often lose from 65 to 75 percent of their body weight. However, the procedure also comes with a high risk of fatality, particularly in patients who are severely obese.

The Massachusetts team, led by Lee Kaplan, performed gastric bypass surgeries on mice, then fed bacteria from those mice's lower intestines to ordinary mice. Those mice lost 5 percent of their body weight over the next two weeks as compared to mice on the same diet who did not receive the bacteria.

Carel le Roux at Ireland's University College at Dublin told New Scientist that the results appear to point scientists toward a possible "knifeless gastric bypass," in which human subjects take a cocktail of bacteria to lose weight.

"It changes how the gut talks to the brain," said le Roux, who was not involved in the Boston study, but who believes that traditional gastric bypass surgery, though effective, can also throw off subtle balances in the body's production of hormones, bile and internal bacteria.

Scientists have theorized that the health of bacteria in the digestive tract can have an impact on cognition, regulating mood control and affecting how well a person handles stress. Some scientists even posit that humans have a "second brain" in the gut, neural tissue that is known as the enteric nervous system.

The enteric nervous system uses many of the same chemical tools as the brain, serotonin and other neural transmitters to regulate itself and to send information up the spinal cord to the brain. These signals could play a role in the weight loss observed in mice who received bacteria from mice who had gastic bypass surgery.

It isn't entirely clear how the transplanted bacteria are causing the weight loss. Some researchers theorize that they reduce the intestines' ability to absorb calories or that they alter the signals associated with metabolism.

The goal, said le Roux, is to find out what's causing the weight loss and to duplicate it by other means.

Transfer of intestinal bacteria isn't entirely new. The procedure has been used to treat symptoms of Parkinson's Disease, multiple sclerosis, chronic fatigue and intestinal infections.

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