A large new study has provided strong evidence that people with brown fat in their bodies are less likely to suffer from a range of health conditions.
"For the first time, it reveals a link to lower risk of certain conditions," says one of the researchers, Rockefeller University Hospital physician Paul Cohen.
"These findings make us more confident about the potential of targeting brown fat for therapeutic benefit."
Brown fat or brown adipose tissue (BAT) is particularly common in hibernating mammals and newborns. BAT helps mammals regulate temperature - when we're really cold, the large amounts of mitochondria found in this type of fat tissue burn energy and produce heat. In fact, the iron-rich mitochondria are what gives brown fat its characteristic colour.
It wasn't until 2009 that scientists discovered some adult humans have brown fat in their bodies as well, usually around the neck and shoulders.
There have been plenty of mouse studies looking at the benefit of having brown fat, but in humans the research has been murkier until recently. Having brown fat seems to improve a person's metabolism and may even help to lose weight (although the latter is probably not quite as simple).
"The natural question that everybody has is, 'What can I do to get more brown fat?'" Cohen says.
"We don't have a good answer to that yet, but it will be an exciting space for scientists to explore in the upcoming years."
The researchers think this might be an underestimation because of the conditions the participants were under - they were told to avoid cold exposure, exercise, and caffeine before the scans, all of which have been linked to brown fat activity.
Around 4.6 percent of those with brown fat also had type 2 diabetes, while that number was 9.5 percent in the 'no brown fat' group. A similar result was seen in abnormal cholesterol results – 18.9 percent of people with brown fat had abnormal cholesterol, compared to 22.2 percent of people who didn't have brown fat.
Hypertension, congestive heart failure, and coronary artery disease also saw small positive differences in the brown fat vs no brown fat groups.
"These findings were supported by improved blood glucose, triglyceride and high-density lipoprotein values," the team writes in their new paper.
While the numbers here are exciting, there's no evidence as yet that brown fat makes you immune to any of these conditions - but there's a link to reduced risk worth exploring further.
What was really interesting though is that brown fat was particularly protective in those that were obese. Those obese patients that had brown fat had similar prevalence of these metabolic and heart conditions as non-obese people.
"It almost seems like they are protected from the harmful effects of white fat," says Cohen.
"Taken together, our findings highlight a potential role for BAT in promoting cardiometabolic health," the researchers note in their paper.
It's important to note that the data the researchers were working with came from cancer evaluations at the Memorial Sloan Kettering Cancer Center, meaning this is not a sample representative of the general population.
Nevertheless, the study has yielded a fascinating new look at the role of brown fat in the human body, and will hopefully lead to even more discoveries in the future.
"We are considering the possibility that brown fat tissue does more than consume glucose and burn calories, and perhaps actually participates in hormonal signaling to other organs," says Cohen.
The research has been published in Nature Medicine.