Why does sunshine make me tired? © Getty Images

Why does sunshine make me tired?

Lazing on a sunny afternoon never sounded like so much effort.

Asked by: Luke Davison, East Grinstead

Advertisement

If you spend time in the sunshine, your body must expend energy to prevent you from overheating. One way it does this is to sweat, which leads to lethargy and dehydration if you don’t drink enough. The more you exert yourself, the more work your body has to do to control your temperature, which makes everything feel like an effort.

The cold makes people feel tired for the opposite reason, as the body must consume energy to stay warm, including through shivering. Bear in mind, though, the Sun doesn’t only make you feel tired. By influencing your circadian rhythm – the body’s internal clock – it also helps you get up in the morning.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.