Three studies appearing in the New England Journal of Medicine indicate that we humans have the stuff too. Why are they just figuring this out now? Because they were looking in the wrong place. In rats, the brown fat is mostly between the shoulder blades, and in human infants, it's a sheet of cells covering the back. But the latest studies show that human adults have brown fat in the upper back, on the side of the neck, in the dip between the collarbone and shoulder and along the spine.

Unlike white fat, which just sits there and annoys you, brown fat pumps out chemicals and hormones that interfere with your health and your ability to fit into your Frankie B's. Brown fat is like a little furnace, burning calories.

If we could only stimulate that brown fat -- and believe me, the drug companies are already working on the problem -- we'd be able to burn more calories without eating differently or even exercising. I'm not sure that's a good thing, but that's another story. The point is, if you are eating well and exercising regularly, stimulating your brown fat might help move things along nicely.

Since Lieberman and Gittleman were both ahead of the curve on this one, it might be worth it to hear their recommendations on natural ways to stimulate brown fat. Gittleman is a fan of evening primrose oil (active ingredient GLA) for just that purpose. And there's even stronger evidence for green tea extract, also known as EGCG.

"Green tea specifically stimulates your body's ability to burn fat in addition to overall calories and stimulates brown fat", says Lieberman. "Studies show that using green tea even without dieting causes weight loss -- so using it with a weight-loss eating plan should give you excellent results."

For more scoop on brown fat, and to find out what it has to do with cold temperatures, check out this AOL Health article.