We don't consider grizzly bears obese, even though they can eat 90 pounds of food and gain 21 inches of fat a day. Now a new study has revealed that grizzlies evolved amazing abilities to cope with the fat they store for hibernation.
For one, the bears safely store large amounts of fat in fat tissue, whereas that same fat in obese humans is stored in the liver and around internal organs, scarring them.
Bears have high cholesterol but they don't develop heart disease like humans do. Humans also tend to get type 2 diabetes when overweight.
That's when the body no longer responds to insulin, the hormone that directs cells to take up sugar from the blood. Over time, elevated sugar levels in the blood cause damage to organs.
In the new study on grizzlies, researchers found that when grizzlies rapidly gain weight each fall, their cells continue to respond to insulin to keep their blood sugar levels stable.
What's interesting is that once grizzlies hibernate, their cells do stop responding to insulin, turning them diabetic. This is so their bodies can control how much energy is being burned during hibernation.
Amazingly, even though they're diabetic during this time, their blood sugar levels remain stable. In the spring, their cells return to normal, which may be explained by a protein both grizzlies and humans share called PTEN.
Obese people with a mutation in their PTEN face a lower risk for type 2 diabetes which mirrors how bears behave! To test that, scientists blocked PTEN in humans and saw improvement to insulin resistance in certain body tissues. The hope is that studying grizzlies whose bodies evolved to solve these biological challenges can one day lead to novel treatments for humans.
For more information…
A Grizzly Answer for Obesity
New York Times discussion of this study by one of the collaborators
PTEN mutations as a cause of constitutive insulin sensitivity and obesity in human beings
Scientific paper regarding PTEN published by Aparna Pal, et al., in the prestigious journal The Lancet
Hibernation videos, news and facts from the BBC
Type 2 Diabetes
Lots of info about this disease from the American Diabetes Association