Why obesity doesn't cause problems for bears

Extensive fat reserves don't make brown bears ill, unlike humans, report Viennese researchers.

Abundant amounts of “good cholesterol” (HDL) and “antioxidants” protect them during hibernation from health-damaging effects.

It may be possible to use the metabolic strategies of Master Petz to combat arteriosclerosis in humans, scientists explain in the journal «Scientific Reports».

A team led by Sylvain Giroud from the Research Institute of Wildlife Ecology at the University of Veterinary Medicine Vienna investigated the cholesterol metabolism and blood values of free-living European brown bears (Ursus arctos) that had built up large fat reserves to avoid starvation during hibernation. During this period, their fat metabolism changed radically, the researchers explain. However, various counter-mechanisms kept the animals healthy despite high blood lipid levels.

Study offers hope for humans

For example, an enzyme in the bears' bodies becomes hyperactive, stabilising HDL cholesterol. This is considered good cholesterol because, unlike LDL cholesterol, it does not cause arterial calcification (arteriosclerosis). In addition, the animals have more antioxidants in their blood. These protect the body from harmful substances (free oxygen radicals) that occur in greater numbers when fat content is excessive and can damage muscles as well as promote inflammation.

Thanks to these protective measures, bears are able to build up fat reserves that would make humans ill. In people, such fat accumulation can trigger arteriosclerosis, along with deposits and inflammatory processes on the inner walls of the coronary arteries, carotid arteries, and leg arteries. This can lead to circulatory disorders in the legs (peripheral artery disease) and medical emergencies such as heart attack and stroke. 

The researchers write that insights from brown bear metabolism could potentially lead to new strategies against arteriosclerosis in humans.