Altering the flow of bile in the mouse gut achieves the same weight-loss benefits as gastric-bypass surgeries.

In a gastric bypass, the stomach pouch is made smaller and connected to the middle of the small intestine. Naji Abumrad at Vanderbilt University Medical Center in Nashville, Tennessee, and his team tested whether the success of such procedures can be replicated by redirecting bile fluids, which break down dietary fat in the upper gut to enable fat absorption. Rerouting the bile duct to the ileum (the lower part of the small intestine) in obese mice resulted in weight loss and other metabolic improvements that were similar to those seen after a gastric bypass. The bile diversion reduced fat absorption and shifted the composition of gut microbes to be similar to that of lean mice.

Redirecting the bile duct in humans would be simpler than gastric bypass, but long-term safety studies are needed, the researchers say.

Nature Commun. 6, 7715 (2015)