Did you know when our bodies are exposed to cold over time, they actually start to change to keep themselves warm?
"We start to build up a tissue ... that we call brown adipose tissue — so brown fat," Dr Dino Premilovac from the University of Tasmania said.
"It's more muscle-like than it is fat-like in what it does.
"If we expose our bodies to the cold environment, the way our bodies deal with it over a long period of time is to produce more brown fat."
Brown fat's purpose in the body is to produce heat to warm up the blood, in turn keeping the body warm.
Brown fat does this by burning up energy, which means it can help burn up the white fat in our bodies that is stored for energy.
Babies a bundle of brown fat
Babies have quite a lot of brown fat to keep their tiny bodies warm, but they tend to lose it as they grown up.
"Up until about four years ago, adults were thought not to have any [brown fat] because there is so little of it in the adult body," Dr Premilovac told Helen Shield on ABC Radio Hobart.
"A lot of the brown fat that we do have is around our shoulders, around our neck and around our heart."
Brown fat has become "sexy", according to Dr Premilovac.
"One way we can increase how much brown fat we have is by cold climate adaptation, so by exposing ourselves to cold climates we can increase how much brown fat our bodies contain," he said.
Keep your shirt on – for now
Exercising in the cold, such as swimming in the open in the middle of winter, can increase the amount of brown fat you have.
But one quick dip is not likely to be effective.
"I would not recommend just going and jumping in the River Derwent," Dr Premilovac said.
"For the average person who just jumps into cold water, you generally don't burn much more fat because you're not trained to actually deal with that cold water."
He said swimming or exercising in the cold only worked to increase brown fat if it was done over a long time and slowly built up your tolerance and exposure.