Turning the central heating down not only saves money but could also keep you slim, scientists claim.
Evidence suggests that being cold may be a healthy and sustainable way to lose weight, experts believe.
Conversely, warm and cosy homes and offices may be contributing to expanding waistlines, it is claimed.
The theory from Dutch scientists follows 10 years of research into the effects of the cold on metabolism.
It suggest that a more variable indoor temperature, one that more closely mirrors temperatures outside, may be beneficial.
At least among young and middle-aged people, non-shivering heat production in response to feeling cold can account for up to 30 per cent of the body's energy budget, say the scientists.
That means lower temperatures can significantly increase the number of calories burned up instead of being stored as fat.
Lead researcher Dr Wouter, from Maastricht University Medical Centre, said: ‘Since most of us are exposed to indoor conditions 90 per cent of the time, it is worth exploring health aspects of ambient temperatures.
One research group in Japan had shown a decrease in body fat after volunteers spent two hours a day at 17 for six weeks, said the Dutch scientists.
The Maastricht team also found that people got accustomed to the cold over time. After six hours a day in the cold for a period of 10 days, levels of heat-generating brown fat in the body increased and people became more comfortable and shivered less.