TEN to 15 minutes of shivering in the cold may be as good as an hour of moderate cycling when it comes to converting energy-storing ‘white fat’ into beneficial energy-burning ‘brown fat’, according to research from the Garvan Institute.

The two activities increase levels of two hormones known to be instrumental in that process —irisin, produced by muscle, and FGF21, produced by brown fat.

People with more brown fat tend to be slimmer and have lower glucose levels than those who have less.

Endocrinologist Dr Paul Lee showed that when 10 healthy adult volunteers were exposed to temperatures cold enough to make them shiver, which occurred between 14°C and 16°C, they produced the same amount of irisin in less than 15 minutes as was produced after an hour of moderate exercise.

“We speculate exercise could be mimicking shivering because there is muscle contraction during both processes, and that exercise-stimulated irisin could have evolved from shivering in the cold,” Dr Lee said.

While 50g of white fat stores more than 1255.2 kilojoules (300 kilocalories) of energy, that amount of brown fat can burn up to the same number of kilojoules, he said.

“White fat transformation into brown fat could protect animals against diabetes, obesity and fatty liver,” Dr Lee said.
But don’t dive into the cool room just yet.

“Cold exposure is a bit like exercise in that perhaps it requires training at the start too, so for instance, you could consider wearing a light jacket rather than a big jumper on a cool day, or not turn the temperature on the heater too high in winter. This is similar to how one would train running shorter distance first before attempting a marathon,” he said.

Cell Metabolism 2014; 19(2):302-309