Active Brown Fat Linked to Lower Risk of Diabetes, Depression and Anxiety in Study of More Than 100,000 People

When people think of fat, they often picture the soft tissue around the abdomen that stores excess calories. That is white fat. Brown fat, by contrast, burns calories and generates heat. It is typically found around the neck, armpits and breasts and has been associated with a range of health benefits.

Fat cells have a ‘memory’ of obesity — hints at why it’s hard to lose weight

A study involving more than 100,000 people suggests that the benefits of brown fat may extend beyond calorie burning. People with “active” brown fat — tissue that switches on and burns calories — were less affected by several health problems, including type 2 diabetes, depression and anxiety, than people without detectable active brown fat.

Researchers used an artificial-intelligence model to quantify active brown fat in participants’ medical scans. They found that greater brown-fat activity was associated with greater protection from disorders and diseases. The study’s results are reported today in Nature.¹

“This is one of the most comprehensive and probably one of the most important studies in this field,” says Shingo Kajimura, a molecular biologist at Harvard Medical School in Boston, Massachusetts.

Because the study is retrospective, however, more research is needed to determine whether brown fat directly causes these health benefits, says Irfan Lodhi, a molecular biologist at Washington University in St. Louis, Missouri. “But it’s still a very interesting and surprising study,” he says.

How brown fat produces heat

Scientists have known for decades that brown fat burns calories and produces heat. The tissue helps newborns stay warm, and scientists once thought it disappeared after babies developed the ability to shiver. In 2009, researchers reported that brown fat is also present in adults.^2,3,4

Why BMI is flawed — and how to redefine obesity

How scientists detect active brown fat

To map active brown fat in people, scientists use imaging techniques that highlight metabolically active tissue. They inject participants with a form of radioactive glucose and then use positron emission tomography (PET) combined with computed tomography (CT) scans. The scans show which tissues take up the glucose and reveal where brown-fat cells are active.

These techniques are also commonly used to diagnose and monitor cancer. A team led by Paul Cohen, a physician-scientist at Rockefeller University in New York City, partnered with Memorial Sloan Kettering Cancer Center in New York to obtain scan data from more than 100,000 people who underwent the procedures during cancer treatment.