We expect to pick up a kilo or two in winter, and we know the cold air can dry out skin. But come summer, how does our body change?
When it comes to the control centre of the body, the brain isn't immune to seasonal changes. Belgian researchers found that depending on the season, the brain allocated its resources differently to perform the same tasks.
As part of the study, participants underwent brain scans while they completed two tasks, one requiring sustained attention and another that required them to exercise their working memory.
While their test scores stayed the same across the seasons, how the brain used its resources differed. In summer, brain activity peaked on the attention tasks, while in winter it fell significantly.
When it came to memory, brain activity peaked in autumn and hit a low in spring. Researchers don't yet know the reasons behind it, but results suggest that the brain adapts its level of efficiency to the time of year.
Far below the surface, the change in seasons also affects our DNA. A study published in Nature Communications found around 5000 genes in the white blood cells change the way they're expressed in response to seasonal changes – up to one-fifth of all genes in the blood cells.
Compared to winter, when your blood predictably contains more immune cells, summer sees more fat-burning and water-retaining hormones enter the bloodstream.
For some skin types, humidity comes with a downside – the combination of heat and humidity can see your sebaceous glands up their oil production, which can lead to more breakouts as the skin becomes more easily congested. But breakouts can also be caused by poor skin cleaning.
As essential as sunscreen is, putting it on and topping it up during the day can clog pores, so make sure you're removing it properly as part of your night-time skincare routine.
Staying hydrated is key to keeping your skin at its best during summer – although you should still keep the moisturiser handy. If you're prone to dry skin, living in a dry climate can make your dry skin even drier – and this can be exacerbated if you're spending a lot of time in air-conditioned environments.
Dry skin can also be triggered by chlorine, which strips the skin of its natural oils, and fake tan, which can contain SD alcohol or ethanol – both of which have a drying effect.
On the bright side, if you live in a humid environment, the moisture in the air can give your skin some much-needed hydration.
Despite eating lighter meals over summer, you're more likely to put on weight during warmer weather as your body holds onto water.
Here's how it works: On an average day, we'll lose and replace around two litres of water. One major sources of water loss is sweat, and the hotter it is, the more we sweat as the body attempts to cool us down. In humid climates, the rate of sweating is even higher as in high humidity the sweat can't evaporate, which negates the cooling effect.
Once the weather starts warming up, the body starts to adjust to higher temperatures through heat acclimatisation. And while we often feel like we couldn't bear it if it got even hotter, the acclimatisation process works very quickly – by the second day, the body begins to sweat more and sooner to cool you down faster.
The downside to this is that the more you sweat, the more water you lose, and so the body begins to increase the total amount of water it holds. Thanks to this, your weight is likely to climb as the body releases hormones like aldosterone, which allow the kidneys to retain more water.
It's important though that you stay well hydrated during hot weather, as dehydration can mess with your metabolism. In the heat, your body slows down slightly to conserve energy in order to stop you from overheating, and dehydrating can slow your system down even more.
A University of Utah study found that when people dehydrate three per cent of their body weight, they saw a two per cent decline in calorie burning per day.
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