Scientists have discovered the protein SLC25A45, which plays a key role in energy conversion in mitochondria - the small power plants of our cells[1][3]. This protein controls the production of carnitine, a substance necessary for burning fat in the body, which is especially important for people who consume plant-based foods with a low carnitine content[1][3]. When the researchers mice lacked this protein, their bodies could not burn fat efficiently and instead relied on burning sugars[1][3]. Such mice were less tolerant to cold and their bodies did not respond properly to weight loss drugs such as GLP-1RAs, which usually promote the loss of adipose tissue[1][3]. The study suggests that mitochondria act as a control point that decides whether the body burns fat or sugar, and this knowledge may have implications for the effectiveness of weight-loss drugs[1][3]. The research was published in the journal Science in January 2026[2].