Brown and White Fat
Brown fat plays an active role in metabolism. ~ American biologist Evan Rosen
There are 2 types of body fat: white and brown. Brown fat is an active form of fat, as opposed to passive white fat. Brown fat cells burn energy and generate heat, regulating body temperature. Brown fat cells are activated by signals that the body is cold. White fat stores energy in the form of lipids.
Mammalian babies, including mice and humans, have pads of brown fat on their backs. Humans lose most of the brown fat in their backside as they grow up.
In adult humans, brown fat is found around the spine, in the abdomen, and in the neck, above the collarbone. Brown fat is far more abundant in healthy humans.
Brown fat helps keep weight off. White fat crowds out brown fat as it provides permanent insulation, making brown fat redundant.