Let’s face it: Fat’s got a rotten reputation. Much of that is deserved, of course. Too much body fat can harm health and lead to heart disease and diabetes.

But to tip the scale just a bit, let’s talk about brown fat.

A new Rutgers University study has found that this distinct type of fat might be key to better aging and exercise performance.

Brown fat is different from the usual white fat that parks around our bellies. White fat stores energy that we burn by being active. Brown fat, however, is chock full of mitochondria, cellular powerhouses that generate heat rather than store energy. It burns calories.

Newborns start life with bodies that have up to 5% brown fat. By adulthood, most of us have far less.

Previous studies have shown that physical activity can increase brown fat’s density. The Rutgers study examined how brown fat can boost athletic performance.

Mice without a protein called RGS14 live longer than others and have more brown fat. In lab tests, the long-lived mice ran farther and worked harder before exhaustion compared with typical mice. And they kept a youthful appearance, with nicer fur and more muscle.

In one study, brown fat was taken from these long-lived mice and transplanted into normal mice. The borrowed-fat mice became better athletes in three days. When scientists placed brown fat from ordinary mice into their test subjects, it took eight weeks to see those gains.

The researchers say brown fat might be the secret to exercising longer while staying pretty doing it. Someday, a brown fat-inspired treatment could help us live healthier and longer.

And if we happen to look younger as we do? Thank a mouse.