Brown fat burns fuel to make heat, and this activity is controlled by the body clock: It drops during sleep and rises before waking. But a cold morning or a skipped meal makes demands the clock never planned for. How the body keeps to a fixed energy timetable while still improvising has long been a puzzle.

Researchers at the University of Copenhagen’s NNF Center for Basic Metabolic Research (CBMR) now show that SLC25A34, a little-studied protein in the mitochondria of fat cells, acts as a switch that connects the body clock, temperature and diet to how fat cells store and spend energy. The study was published in Science.

“We usually think of the body clock, the response to temperature and the response to food as separate systems. A mitochondrial transporter that is tuned by the⁰ time of day, the temperature and what we eat) raises the possibility of therapies that shift when and how the body burns fuel. That would be a different kind of lever from today’s obesity and diabetes treatments,” says corresponding author Zach Gerhart-Hines, an associate professor at CBMR.