New research indicates that gut microbes help mediate the benefits of short-term exposure to cold, which is known to mimic some of the effects of exercise (Chevalier C et al. Cell. 2015;163:1360-1374.)
A team led by researchers at the University of Geneva in Switzerland found that cold exposure (6°C or 43°F) for up to 10 days dramatically altered the composition of intestinal bacteria in mice. Transplanting such “cold microbiota” to germ-free mice was sufficient to increase insulin sensitivity, energy expenditure, and fat (or adipose) loss. The effects occurred in part because of a switch from energy-storing white adipose tissue to energy-burning brown adipose tissue.
After long-term cold exposure, however, fat loss was attenuated by adaptive intestinal expansion through increased intestinal, villi, and microvilli lengths. Transplantation of cold microbiota into germ-free mice was alone able to increase intestinal absorptive surface in these mice. This suggests that gut microbes may enable mammals to harvest more energy from food during prolonged cold exposure as a way to protect against hypothermia.