You may have heard the idea that if you expose yourself to a bit of cold then your body will expend some energy to keep you warm and therefore you could burn some of that spare tyre. But did you know that those helpful bacteria that live in your gut are directing some of the response?
Reported in the journal Cell, researchers exposed mice to cool temperatures and then looked at the effect this had on their metabolism. They also took the gut bacteria from these mice and put them into mice that had no bacteria in their gut. As a control they did the same with bacteria from mice that had not been exposed to cold.
It seems that after a cold spell, the bacterial composition changed. When these bacteria were seeded into the germfree gut of another mouse, that mouse had increased insulin sensitivity. It also encouraged the conversion of white fat cells to beige fat. This type of fat uses energy to produce heat and therefore increases energy expenditure and fat loss. These changes were not observed in the control mice that were given bacteria from non cold treated mice.
The researchers say that this demonstrates that the microbiota (the gut flora) are key to the body adapting to cold.
But before you run to the freezer to try and slim down a bit, prolonged cold treatment causes the gut to increase in size allowing more energy from the food passing through to be absorbed and therefore attenuating the weight loss effect.