Scans of 100,000 Patients Link Active Brown Fat to Better Metabolic Health

The work was published in Nature in 2026. It is an observational study in people, not a trial. Researchers drew on a cohort of 101,243 patients at a large cancer centre. They also ran a proof-of-concept test of the drug losartan, which the study reports increased brown fat cell activity and whole-body energy expenditure. Observational data can show that two things go together. They cannot show that one causes the other.

Brown fat is different from the white fat that stores energy. Brown adipose tissue uses energy to produce heat. Earlier work had linked detectable brown fat in humans to a lower prevalence of cardiometabolic disease, meaning conditions that affect the heart and metabolism. What was missing, the authors write, was a full picture of which health conditions it relates to, and a fast way to measure how active the tissue is in many people.

The team used big data and artificial intelligence to fill that gap. In an unbiased sweep across all diagnoses, cardiovascular and psychiatric diseases were less prevalent in people with brown fat. Then a machine learning approach semiautomatically measured brown fat activity in about 8,700 patients.

Higher activity was tied to lower odds of cardiometabolic disease and to a healthier distribution of white fat. This was especially true for brown fat in the axillary depot, the area around the armpit. People with brown fat also had more favourable blood sugar measures, lipid profiles, inflammatory markers and echocardiographic indices, which are measures taken from heart ultrasound.

The medication analysis produced the headline-friendly result. Use of angiotensin receptor blockers, a class of blood pressure drugs, was positively associated with having brown fat. As a proof of concept, the authors showed that one of them, losartan, increased brown fat cell activity and whole-body energy expenditure.

News-Medical, summarising a Rockefeller University release, reports that the energy findings came from experiments in cultured cells and in healthy mice, which kept a steady body weight. It also quotes first author Nicolás Gómez-Banoy saying losartan acts on brown fat through different molecular pathways than its blood pressure effect. That could, he says, allow future therapies to stimulate brown fat in people with normal blood pressure.

That is why the drug link is not a reason to take losartan. The human data show only that people on these drugs were more likely to have brown fat. They do not show that the drug created it, or that taking it would improve anyone's health. Losartan is a prescription medicine for people with a medical need. The study frames its result as a platform for drug repurposing, not as a recommendation.

The mental health finding also needs care. Gómez-Banoy told News-Medical that metabolically healthy people tend to have lower rates of psychiatric disease, so brown fat may simply track with better metabolic health. The coverage also reports that SSRI antidepressants were associated with dampened brown fat activity, and that the researchers want to look at possible downsides, including osteoporosis and skin disease.

Other limits matter too. The patients were being monitored for cancer, so they may not represent the general public. This is also where the argument is weakest: an association in a single hospital cohort cannot say whether brown fat improves health, whether it is a marker of it, or whether drugs shape it.

For now, the practical message is modest. Brown fat looks like a marker of metabolic health, and this study gives researchers a way to measure it at scale. Watch for work that tests whether activating brown fat in people improves health outcomes, and whether other drugs flagged in the data do the same. Senior author Paul Cohen told News-Medical, "This is just a start."

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