We were to expose ourselves to cooler temperatures more often, then a lot of people would probably lose weight,' he says.
'Either that or have a daily sauna and plunge into icy water afterwards. Don't have the heating on in the car and spend more time outdoors, especially in winter. Warmer temperatures, abundant food and too little activity have effectively switched off its usefulness in the modern world. 'Even 30 years ago, it was more difficult to stay warm than it is now,' says Professor Cawthorne. In evolutionary terms, brown fat developed to protect newborn babies from lifethreatening cold temperatures. It is thought that, in a throwback to our ancestors, chilly conditions trigger brown fat to become activated in adults.