A new study in Cell reports that the bears underwent genetic changes to allow them to eat their high-fat diets and survive in the Arctic. Genes related to the bears' cardiovascular and metabolic systems changed through mutations to allow them to pig out on fatty foods without having a high risk for heart disease.
The bears have high levels of triglycerides and LDL (bad) cholesterol. That would cause heart disease in humans, but the bears' genetic changes have made the bears able to survive despite the diets. The scientists noted a change in the gene APOB, which transports cholesterol out of the bloodstream and into cells — reducing the bears' risk for heart disease.
The scientists also found that the species diverged from brown bears less than 500,000 years ago, so it's newer than we originally thought.
"For polar bears, being very fat is no problem," said Eline Lorenzen, a molecular ecologist at the University of California, Berkeley. Polar bears can be about 1,700 pounds.
Up to half of a polar bear's body weight can be fat and their source of fresh water is metabolic water that is a byproduct of the breakdown of fat in the body.
The researchers examined blood and tissue samples from 79 polar bears from Greenland along with samples from 10 brown bears.
"In this short amount of time, polar bears have adapted to the cold environment of the Arctic and to a new diet. We see the footprints of this adaptation in the genome of the polar bear," said Rasmus Nielsen, an evolutionary geneticist at the University of California, Berkeley.
OK, maybe we don't want to live on a high-fat diet (though we're not opposed to the occasional indulgence). Just don't overdo it — we definitely do not have the genetic capabilities to handle too much.
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