Bears also shut down their renal function during hibernation, resulting in badly scarred kidneys and high levels of blood toxins that would kill a human. What is truly remarkable is that the bears’ kidney failure is reversible: Upon awakening from hibernation, their kidney function is fully restored with no lasting damage.

These observations make bears a veritable cornucopia of biological discovery. The problem, of course, has been to figure out how to practically and safely study 700-pound animals with uncommon strength and a reputation for being surly.

Luckily for me, Charles T. Robbins at Washington State University has spent 28 years working out how to house rescue grizzlies and have them hibernate in captivity. Collaborating since 2011, we have discovered some fascinating features of bear metabolism that may lead to valuable innovations in treating obesity. (My company has invested in our research.)

We started by asking if the unparalleled gains in weight and body fat necessary to survive hibernation are accompanied by consequences, like diabetes, that are typically observed in humans. The type of diabetes associated with human obesity is a result of the body’s inability to respond to the hormone insulin and so is referred to as “insulin resistance.”

In a healthy human, an injection of insulin will cause a drop in blood sugar as the hormone facilitates the transport of sugars from the blood into cells, where it is either used to produce energy or stored as fuel. In a diabetic subject, the cells fail to respond to the insulin and their blood sugar stays high — with long-term effects like obesity, hypertension and cardiovascular disease.

But bears are able to modulate their insulin responsiveness, so that when they are most obese, in the fall, they are most insulin sensitive. In other words, even as they pile on the pounds, their cells retain the capacity to take instructions from insulin.

Just weeks later, the bears render themselves completely insulin resistant while in hibernation; they become, in essence, diabetic. But hibernating bears differ from diabetic humans in that they maintain normal blood sugar levels while in this insulin-resistant state. Once they wake, in the spring, the grizzlies restore their insulin responsiveness. So bears modulate insulin sensitivity not to maintain normal blood sugar levels but to control when fat is stored and when it is broken down.