Obesity may not keep body warm, mouse study finds

In contrast to popular belief, carrying extra fat may not play a role in keeping warm, according to an article published in the American Journal of Physiology - Endocrinology and Metabolism

According to the Centers for Disease Control and Prevention (CDC), more than one third of adults in the United States are obese.


Although there is interest in the connection between metabolism and obesity, there is still little known about the extent to which obesity affects metabolism.

There is also little known about whether the development of obesity may be aggravated if excess fat insulates against heat loss, resulting in a decrease of food burned for body temperature control.

The new study on the insulating effect of obesity, by researchers from Stockholm University in Sweden and the University Medical Center Hamburg-Eppendorf in Germany, finds that it is in fact fur, not carrying excess fat, that contributes to a warmer body in obese mice.

"Whether an insulating effect of obesity exists is of significance both for humans and for animal models of obesity," the research team writes.

The findings from this study are significant for obesity researchers to grasp how body fat functions to keep mice warm. Mice used for metabolic research are frequently accommodated in cooler conditions, and almost half of the calories they consume are burned to maintain body temperature.

Fur responsible for nearly 50 percent of insulation
The team conducted several experiments to observe the way temperature and insulators, such as fat and fur, affect metabolism. The researchers write:

"In contrast to established views, we demonstrate here that at least in mice, obesity is not associated with increased insulation, and obesity thus does not in this way affect the metabolism of mice."

The results reveal that fur is associated with increased insulation, protects against heat loss, and is responsible for almost half of a mouse's insulation.

The findings conclude that obesity of any kind does not increase thermal insulation in mice or aggravate the development of obesity.

Equivalent insulation studies have not yet been performed in humans. However, with the use of clothing and adjusting indoor temperatures, humans are usually in an environment where the body can maintain its core temperature solely through regulating heat loss to the external environment.


The researchers indicate that "it is doubtful that an insulating effect of obesity, even if it existed, would in any discernable way affect the development or maintenance of human obesity."