A common blood pressure medication may have an unexpected effect on metabolism. In an NIH-funded study published October 14, scientists discovered that losartan activated calorie-burning brown fat in mice. But despite burning more energy, the animals didn’t lose weight.
The findings, published in Nature, followed an analysis involving more than 100,000 patients. Researchers identified connections between brown fat activity, cardiovascular health, and mental health, raising questions about what this overlooked tissue might do beyond regulating body temperature.
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Why This Type of Body Fat Has Scientists Excited
Unlike white fat, which stores excess energy, brown fat burns energy to generate heat. Researchers believe activating this tissue could eventually offer new approaches to metabolic disease.
Using artificial intelligence to examine medical imaging, scientists identified associations between greater brown fat activity and better cardiometabolic health.
They also observed lower rates of anxiety and depression among patients with more brown fat. These findings establish associations, not proof that brown fat prevents psychiatric conditions.
Rockefeller University researcher Paul Cohen, MD, PhD, explained that expanding the investigation revealed previously overlooked connections.
“The scope of this new analysis is far more expansive,” Cohen said in the NIH announcement. “We doubled our number of patients and considered more than 500 codes, which allowed us to unearth many new insights.”
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The Blood Pressure Drug Produced an Unexpected Result
Researchers noticed that patients taking angiotensin receptor blockers, a medication class that includes losartan, showed greater brown fat activity.
Laboratory experiments subsequently demonstrated that losartan directly stimulated brown fat cells. Treated mice consumed more oxygen and expended more energy, yet maintained stable body weight.
Importantly, the researchers identified molecular mechanisms distinct from those responsible for lowering blood pressure.
“The fact that its different effects are mediated by different molecular pathways is advantageous,” said lead author Nicolás Gómez-Banoy, MD.
He added that researchers might eventually develop therapies that stimulate brown fat without affecting normal blood pressure.
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What This Means for Weight Loss
The findings don’t establish losartan as a weight-loss medication. The metabolic experiments involved cells and mice, not a human trial demonstrating fat loss.
Still, the discovery opens another avenue for investigating metabolic and cardiovascular treatments.
“There were plenty of other medications associated with brown fat activity in our large cohort,” Cohen said. “This is just a start.”
For now, patients shouldn’t start or change blood pressure medication to influence metabolism. The real breakthrough is identifying a potentially useful biological target, not discovering a shortcut to losing weight.
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