To deal with cold environments, mammals have several options. They could produce heat by increasing metabolism or shivering or they could conserve heat by constricting blood vessels in their skin or snuggling with a friend or insulating materials. With this in mind, researchers wondered how varying levels of insulation (obesity, fur) in mice affected heat loss and how much energy the animals used to maintain body heat. Their thinking was that more insulation would prevent heat loss and lower energy needs. Sounds logical, right?
This reasoning was indeed logical for the amount of fur an animal had. Mice with shaved fur did have increased metabolism compared to those with normal body hair. What was surprising to the researchers was that obesity was not at all related to preventing heat loss in the mice. In fact, obese mice lost just as much heat as non-obese mice.
Fischer AW, Csikasz RI, von Essen G, Cannon B, Nedergaard J. No insulating effect of obesity.