Study among 50,000 people finds that brown fat can protect against numerous chronic diseases

Brown fat is the magic tissue you want more of. Unlike white fat, which stores calories, brown fat burns energy and scientists hope it could be the key to new obesity treatments. But it has long been unclear whether people with enough brown fat really enjoy better health. First, it was difficult to identify even such individuals, as brown fat was hidden deep in the body.

Now, a new study in Physical Medicine This provides strong evidence: among more than 52,000 participants, those with detectable brown fat were less likely to have heart and metabolic conditions, ranging from type 2 diabetes to coronary artery disease, which is the leading cause of death in the United States.

The study, by far the largest of its kind in humans, confirms and magnifies the health benefits of brown fat suggested by previous studies. “For the first time, it reveals a link to lower risk for certain conditions,” said Paul Cohen, Albert Resnick, MD, assistant professor and senior attending physician at Rockefeller University Hospital. “These findings make us more confident about the potential of targeting brown fat for therapeutic benefit.”

A valuable resource

Although brown fat has been studied in newborns and animals for decades, scientists only appreciated in 2009 that it also occurs in some adults, usually around the neck and shoulders. From then on, researchers scrambled to study the elusive fat cells, which have the power to burn calories to produce heat in cold conditions.

However, large-scale studies of brown fat were practically impossible because this tissue appeared only on PET scans, a special kind of medical imaging. “These scans are expensive, but more importantly, they use radiation,” said Tobias Becher, the study’s first author and former clinical scholar at Cohen’s laboratory. “We do not want to subject many healthy people to it.”

A doctor-scientist, Becher came up with an alternative. Across the street from his lab, many thousands of people visit Memorial Sloan Kettering Cancer Center to undergo PET scans for cancer evaluation. Becher knew that when radiologists detect brown fat on these scans, they regularly take note of it to make sure it is not confused as a tumor. “We realized that it could be a valuable resource to start us looking at brown fat on a population scale,” says Becher.

Protective grease

In collaboration with Heiko Schoder and Andreas Wibmer at Memorial Sloan Kettering, the researchers examined 130,000 PET scans of more than 52,000 patients and nearly 10 percent of the individuals found the brown fat. (Cohen notes that this figure is probably an underestimation, because the patients were instructed to avoid exposure to cold, exercise, and caffeine, which presumably increases brown fat activity).

Several common and chronic diseases were less common among people with observable brown fat. For example, only 4.6 percent had type 2 diabetes, compared with 9.5 percent of those who did not have detectable brown fat. Similarly, 18.9 percent had abnormal cholesterol, compared with 22.2 percent in those without brown fat.

In addition, the study revealed three other conditions for which people with brown fat have a lower risk: hypertension, congestive heart failure and coronary artery disease – links that have not been observed in previous studies.

Another surprising finding was that brown fat can mitigate the negative health consequences of obesity. In general, obese people have an increased risk of cardiovascular and metabolic conditions; but the researchers found that the prevalence of these conditions among obese people with brown fat was similar to that of non-obese people. “They almost seem to be protected from the harmful effects of white fat,” Cohen says.

More than an energy-burning power station

The actual mechanisms by which brown fat can contribute to better health are still unclear, but there are some clues. Brown fat cells, for example, consume glucose to burn calories, and this can potentially lower blood glucose levels, a major risk factor for developing diabetes.

The role of brown fat is mysterious in other conditions such as hypertension, which is strongly linked to the hormonal system. “We are considering the possibility that brown adipose tissue does more than consume glucose and burn calories, and perhaps also participate in hormonal signaling to other organs,” says Cohen.

The team plans to further study the biology of brown fat, among other things by searching for genetic variants that may explain why some people have more of it than others – possible first steps to develop pharmacological ways to stimulate brown fat activity around obesity and related conditions to treat.

“The natural question everyone has is, ‘What can I do to get more brown fat?'” Cohen says. “We do not yet have a good answer to that, but it will be an exciting space for scientists to investigate in the coming years.”