Although it might be easy to assume that your chubbiest, hairiest friend will be much better off in the depths of winter, the science on being cold is actually a bit more complex than that.
Firstly, feeling cold and actually being cold are two different things. Our brain responds to a change in temperature, so even when there’s a sudden drop – like if you jump into a freezing pool – our bodies can prevent a drop in core body temperature for over an hour.
But that doesn’t mean you won’t feel really cold right after you jump in.
“The main reason that we feel cold in the first place is due to receptors that are sensitive to cold, [which] are in the skin,” says Ollie Jay, researcher of physiology at the University of Sydney.
“It will depend on what parts of the body are exposed to the cold, but there are also other things that determine if people physically cool quicker.”
Not just fat layers
The reason why we experience the cold differently is due to a mix of shape, size, age and gender influences.
Although your fatter friend might have a slight advantage in the cold, it’s actually general body size, rather than fat, that correlates with how warm you can keep. Because we generate heat within and lose it from the surface, the body mass-to-skin ratio comes into play, with bigger people generating more heat while losing less.
“If something is bigger and you’re waiting for it to cool down, it will take longer to cool down because the heat sink is larger. That is a benefit for people who are heavier, but they don’t have to have higher fat,” says Jay.
However, fat can play a small role. “All things being the same, if you have the same body size, and have different levels of fat, in the cold it will serve as an insulator, because you have vasoconstriction in the skin.”
Anecdotally, women seem to complain about being cold more, and that could well be because on average they have smaller bodies than males do.
Your experience of cold can also have genetic influences. A twin study found that the feeling of cold in hands and feet is highly heritable, meaning that the basis for feeling excessively cold could be inherited from your parents.
Your head is not the hottest
What about that idea that you lose most of your heat from your head? Well, that is definitely a myth, which came about because of a study in the 1950’s that made people completely cover up, apart from their head.
“That is only relevant if you are completely bundled up,” says Jay. “If everyone was naked, then of course you wouldn’t lose 90% of your heat through your head, you would lose far more heat elsewhere, and the only reason that you would lose that much heat is if that was the only bit that is exposed.”
“If you had everything covered but no shoes, you would lose 100% of your heat from your feet.”
Finally, it seems that if we are healthy but still cold all the time, it’s probably our own fault. Most of us have become accustomed to feeling comfortably warm more often than not. Instead of our metabolism doing its job, we use external factors to keep warm, like heaters and expensive clothes, which could even be contributing to obesity.
So maybe we should all keep wearing our shorts a little longer.