Brown Fat Cures Cold

Investigating how brown fat works in mice, a team of researchers at the University of California, San Francisco (UCSF) has uncovered what may be a holdover from our evolutionary past: in response to cold, tiny immune cells known as macrophages can switch on the brown fat, inducing it to burn energy to make heat.

Unlike ordinary "white" fat, in which the body stores excess calories, brown fat can burn calories to heat up the body. It's one of the things that helps keep wild critters warm on cold nights.