Brown Fat Linked to a Healthier Body and Mind
A pill that millions of people take for high blood pressure may also switch on the body's heat-burning fat. That lead came out of the largest study of human brown fat so far, in which researchers used AI to analyze PET/CT scans from more than 100,000 patients and found that active brown fat is linked with less cardiometabolic disease, anxiety and depression.
Key Takeaways
- An AI analysis of scans from more than 100,000 cancer patients links active brown fat with fewer cardiometabolic conditions, including type 2 diabetes, and with lower rates of anxiety and depression.
- Of the body's six brown fat depots, activity in the armpit showed the strongest tie to cardiometabolic health.
- The blood pressure drug losartan raised brown fat activity in cells and energy use in mice, but the human findings show correlation, not cause.
A Shortcut Through Cancer Scans
Brown fat burns energy to make heat, while ordinary white fat stores it. The tissue is hard to study in people because it shows up clearly only on PET scans, which doctors rarely order for healthy volunteers.
The team found a workaround in cancer care. A group led by Paul Cohen at Rockefeller University worked with Heiko Schöder and Daniel Lafontaine of Memorial Sloan Kettering Cancer Center. Together they studied PET/CT scans and medical records from more than 100,000 patients imaged during cancer treatment and surveillance.
That cohort doubles the size of the group's 2021 study of roughly 50,000 patients, which tied brown fat to lower odds of conditions such as coronary artery disease and type 2 diabetes. This time, AI tools semi-automatically measured brown fat activity across the whole body and in each depot. The researchers then screened more than 500 diagnostic codes without choosing targets in advance.
Links Beyond Metabolism
People with active brown fat had better cardiometabolic health, and the link grew stronger as activity rose. The analysis also found associations with other organ systems, including lower odds of respiratory failure and ascites, a buildup of fluid in the abdomen.
Mental health showed up too. Patients with brown fat had lower rates of anxiety and depression.
First author Nicolás Gómez-Banoy, an instructor of clinical investigation at Rockefeller and an endocrinologist at Weill Cornell Medicine, offered one possible explanation.
“We know that metabolically healthy people tend to have lower incidence of psychiatric diseases, so it could be that having brown fat makes you more metabolically healthy, and this correlates with fewer psychiatric issues,” he said.
Location made a difference as well. Brown fat appears in six regions of the body, including the neck, the armpit and the tissue around organs such as the heart and kidneys. Activity in the armpit depot showed the strongest link to cardiometabolic health.
Clues in the Medicine Cabinet
Because the scans came with full medical records, the team could check how common drugs lined up with brown fat. Metformin was linked to less brown fat, even after accounting for diabetes. The antipsychotic olanzapine, which promotes insulin resistance, was linked to more. SSRIs, widely prescribed for depression, appeared to dampen brown fat activity.
Patients taking angiotensin receptor blockers, a class of blood pressure drugs, showed higher brown fat activity. The researchers then tested one of them, losartan. In cultured brown fat cells, it raised metabolic activity. In mice, it increased energy expenditure and oxygen consumption without changing body weight.
Losartan has a well-known safety profile, so repurposing it could become a practical way to stimulate brown fat. Cohen sees more candidates waiting in the data.
“There were plenty of other medications associated with brown fat activity in our large cohort. This is just a start,” Cohen said.
What the Data Cannot Prove
The study looks back at existing scans and records. It shows associations, not proof that brown fat prevents disease. The data also hinted at possible downsides, including higher rates of osteoporosis and skin diseases among people with brown fat.
The National Institutes of Health funded the work and highlighted losartan as a possible way to activate the tissue. Still, the human results remain observational, and the drug evidence so far comes from cells and mice. Big data sets keep exposing links between body systems that small trials miss, as a recent study of abrupt changes across body systems at menopause also showed.
Drug developers have chased brown fat for years because it burns blood sugar and fat to produce heat, with cold as its classic trigger. Earlier NIH-backed research found that brown fat also clears certain amino acids from the blood after cold exposure. A pill that mimics cold, without the shivering, would give that research a direct route into the clinic.
Written by Alius Noreika