The function and distribution of adipose tissue in the body change during the course of life. Beige fat cells, a special type of adipocytes, have the capability to use energy reserves – fatty deposits – by generating heat in a process known as thermogenesis. With increasing age, beige adipocytes take on the morphology of white adipocytes. Thermogenic activity ceases and with it the cells’ ability to burn fat. As a result, the risk of obesity increases. A team has now proven that the epigenetic enzyme lysine specific demethylase 1 (Lsd1) plays a key role in this transformation.