Disrupted sleep patterns alter the composition of gut bacteria, leading to metabolic problems.

Eran Elinav at the Weizmann Institute of Science in Rehovot, Israel, and his team found that the abundance of gut microbes in mice fluctuates daily in sync with host feeding times. But when the team genetically disabled the animals' circadian clocks or shifted them by eight hours, the bacteria lost this rhythmicity and their composition changed.

Jet-lagged mice eating a high-fat diet gained more weight and showed an increased susceptibility to diabetes compared with normal mice that were fed the same food. Jet-lagged humans had more bacteria called Firmicutes — which have been linked to metabolic disease — in their guts than before their transatlantic trips.

The findings could explain why shift workers have a higher risk of obesity and diabetes.

Cell http://doi.org/wfh (2014)