Why does sunshine make me tired?

Asked by: Luke Davison, East Grinstead

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.

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