Tirzepatide, the drug sold as Mounjaro and Zepbound, is known to reduce weight largely by suppressing appetite. New research from the University of Barcelona suggests it may also act directly on metabolism by activating brown adipose tissue, a type of fat that burns energy rather than storing it.
In the study, obese mice on a high-fat diet received tirzepatide and were compared with control mice fed the same amount of food. Because food intake was matched, the observed activation of brown fat could be attributed to the drug itself, not to eating less. The researchers also observed production of batokines, molecules released by brown fat that are considered metabolically beneficial.
The findings point to a broader strategy for obesity treatment: combining appetite reduction with increased energy expenditure. Previous attempts to activate brown fat with drugs have been limited by side effects, particularly cardiovascular ones. The researchers note tirzepatide did not show those negative effects in mice, but they caution that human metabolism and fat distribution differ, so clinical confirmation is needed.