Biochemist Kevin Corbit had a question: Why don't fat bears get diabetes or other diseases as they bulk up for winter? In humans, obesity is considered a primary risk factor for type 2 diabetes, but grizzlies, as Corbit points out to Science, don't get diabetes.
The answer, according to a new study published today in Cell Metabolism, is that a cellular switch helps grizzly bears recover from potentially diabetic conditions. When obese bears hibernate, a biochemical signal keeps the grizzlies' fat cells from becoming desensitized to the hormone insulin. Humans, on the other hand, don't have this switch -- and as we lose the ability to respond to insulin, our bodies release too much blood sugar, resulting in type 2 diabetes.
Leading up to the colder months, grizzlies pack on the pounds, eating up to 58,000 calories a day (that's the caloric equivalent of about 100 Big Macs). After a few weeks of hibernation, bears begin to show signs of insulin resistance. But by the time the bears wake up in springtime, their cellular switches have been flicked. The grizzlies are once again more sensitive insulin -- it's as if the bears had averted becoming diabetic.