NEW YORK (CBSNewYork) – Could coffee help fight diabetes and obesity? New research shows drinking a cup of coffee can stimulate what is known as “brown fat” that your body uses to keep you warm by burning calories.

Normal fat stores energy, while brown fat has lots of mitochondria which have iron, which is why it’s brown, according to CBS News Medical Contributor Dr. David Agus.

Since its purpose is to generate heat, the goal is to stimulate brown fat. Exercise stimulates brown fat, good sleep stimulates brown fat, and now we know caffeine or coffee can do the same.

A study published in Scientific Reports is one of the first to be carried out in people, reports CBS2’s Marc Liverman.

Previous research shows drinking coffee may have many health benefits, including a lower risk of diabetes, cardiovascular disease and death. But too much may not be a good thing.

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“Up to three cups a day may have a health benefit, no detriment,” said Agus. “Don’t do more, so more isn’t better.

“What I also want to push is no coffee after 1 or 2 p.m,” he said. “Coffee’s half life is six hours so if you have a 1 p.m., still it’s only going to be half the level by 7 p.m. and so even if you sleep, it’s not going to be the deep restful sleep with caffeine on board.”

Researchers are now studying caffeine supplements to see whether the effect on brown fat is similar.

Experts say people who drink more than four cups of coffee a day may want to cut back if they are suffering side effects such as headaches, insomnia and nervousness.