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Extra Fat Does Not Keep Obese Mice Warmer, Research Finds

Fur, not fat, plays the greatest role in keeping obese mice warm

by American Physiological Society
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Bethesda, Md. —Carrying excess fat does not contribute to a warmer body in obese mice, a new study on the insulating effects of fat finds. The article is published in the American Journal of Physiology—Endocrinology and Metabolism.

obese mouse model versus regular mouseResearchers have found that, at least when it comes to mice, obesity does not play a key role in keeping the body warm.Photo credit: Bigplankton and Sunholm, Wikimedia Commons“Whether an insulating effect of obesity exists is of significance both for humans and for animal models of obesity,” the research team wrote. Understanding how body fat works to keep mice warm is particularly important for obesity researchers. Mice used for metabolic research are often housed in cooler conditions. Nearly half of the calories they consume are burned to maintain their body temperature.

The researchers ran several different types of experiments to observe how temperature, fat, and other insulators, such as fur, affected metabolism. “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 researchers wrote. What did work to keep the mice warm was fur. The research team found fur to be a significant protector against heat loss, responsible for roughly half of a mouse’s insulation.

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Whether these findings would be equivalent in humans has yet to be studied. However, by wearing clothes and adjusting temperature indoors, humans are normally in a temperature-neutral environment. “Therefore,” the researchers wrote, “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. At thermoneutrality, no extra food combustion is required to counteract heat loss, and the degree of insulation would thus not play any role for the metabolic balance equation for normal-life humans.”

The article “No insulating effect of obesity” is published in the American Journal of Physiology—Endocrinology and Metabolism. It is highlighted as one of this month’s “best of the best” as part of the American Physiological Society’s APSselect program. Read all of this month’s selected research articles on the APSselect website.