Being cold could be the key to losing weight this winter, thanks to a special type of fat called brown fat. Unlike white fat, which stores energy, brown fat converts calories into heat when we are cold. In theory, turning down the thermostat or taking a cold water swim could boost the benefits of brown fat.
However, experts caution that it may not be as simple as taking a cold plunge. Brown fat is abundant in babies, who lack sufficient muscle to shiver, but adults have far less. Martin Whyte, associate professor of metabolic medicine at the University of Surrey, told The Independent: “Adults have a relatively small amount of brown fat and there’s no real way of boosting its numbers. You could use the brown fat that is already there but it's not going to have a dramatic effect on energy balance.”
What is possible is the “browning” of white fat cells into beige fat, which behaves similarly to brown fat. This requires persistent cold exposure—at least a couple of hours a day at around 16°C. The cold triggers the release of noradrenalin, which binds to receptors and leads to browning. However, prolonged cold also increases appetite, potentially leading to weight gain.
Medication could replicate the effects without cold exposure, but such drugs might increase heart rate. Adam Collins, associate professor of nutrition at the University of Surrey, noted that while there is an association between browning and weight loss, causation is not proven. He suggested that those with more brown fat may simply be more tolerant of cold, rather than having a metabolic advantage.
