In mice, a type of gut bacteria called Sphingomonas paucimobilis moves to belly fat during inflammation and blocks the body’s ability to burn calories for heat by interfering with a key fat-burning chemical and its signaling pathway.

When scientists grew fat cells with this specific bacteria (Sphingomonas), the cells stopped making a key fat-burning chemical and heat-producing proteins—but when they used a different common bacteria (E. coli), nothing changed.

When scientists gave a specific fat chemical (15-HETE) to mice whose heat production was blocked, it brought back their ability to burn fat and generate heat, even if the bacteria or enzyme blocking it were still present.