Intestinal microbes promote fat breakdown in the cold

Exposure to the cold promotes weight loss by stimulating the activity of brown body fat. Brown adipose tissue is a special type of tissue that releases energy in the form of heat instead of storing this energy in the form of fat. Brown adipose tissue becomes more active in response to the activity of specific types of microbes in the gut.

Swiss scientists from the University of Geneva found in a study with rats that cold changed the composition of gut microbes, increasing insulin sensitivity and converting white fat cells into brown fat cells. The activity of these gut microbes could explain why exposure to cold promotes fat loss.

Viruses and bacteria affect food absorption and digestive tract hormones that regulate appetite and metabolic rate (the rate at which you burn calories). Animals infected with a common human cold virus put on much more fat than animals that were not infected. The same viruses were more prevalent among overweight people, which means there could be a link.

The Pennington Medical Research Center in Louisiana, a leading center for obesity research, has even established a virus and obesity unit.

(Cell, 163: 1360 - 1374, 2015)