Ingesting genetically engineered bacteria helps obese mice to lose weight by altering their metabolism.

Sean Davies at Vanderbilt University in Nashville, Tennessee, and his colleagues engineered Escherichia coli to produce chemicals called NAPEs, which the body converts into lipids that signal fullness. When the researchers gave these bacteria to mice on a high-fat diet, the animals ate less, gained less weight and were more sensitive to insulin than were mice that did not receive the bacteria.

These effects were maintained for at least four weeks after the bacteria were removed from the animals' drinking water, suggesting that the microbes were incorporated into the gut flora. The approach could be used as a long-term treatment for chronic conditions such as obesity, the authors say.

J. Clin. Invest. (2014)