Brown fat, the fat cells that help mammals regulate their body temperature, could become a target for weight-loss drugs, thanks to a discovery by Berkeley researchers. The multidisciplinary team, including bioengineering professor Sanjay Kumar in collaboration with Andreas Stahl from nutritional sciences and toxicology, has identified the specific biochemical pathway that activates brown fat and causes the body to burn more calories. The researchers learned that when the brain releases norepinephrine, brown fat cells stiffen, triggering a series of signals that end with these cells soaking up fat and sugars from the diet and burning them for heat. Furthermore, they determined the key role in this process played by myosin – a protein also found in muscle cells – which stiffens brown fat cells. As a test, the team used a drug to increase tension in brown fat cells and were able to show that this approach can lead to the burning of more calories. Future work will be focused on finding the right chemical compound to do this effectively.