In tense days or during periods of mental load, many of us sleep less. Sometimes it is because of stress, sometimes because we wake up in the middle of the night, and sometimes simply because it is hard for us to fall asleep. So yes, we have all felt it – lack of sleep does not only cause a feeling of tiredness in the morning.
It affects almost every system in the body, and sometimes lack of sleep for one night weakens us for several days afterward. But if it is several consecutive nights of lack of sleep? Studies have proven that it affects appetite, blood sugar levels, brain function, the body’s response to stress and even the accumulation of fat in the abdominal area.
How many hours of sleep are considered enough? And is it the same number for all of us? According to recommendations of sleep medicine organizations, most adults need at least 7 hours of sleep per night on a regular basis in order to maintain health. But there is another issue here – not only the duration of sleep is important, its quality as well.
There is no point in measuring when we went to sleep and when we woke up in the morning, but only whether the sleep is relatively continuous, without many awakenings. Only in this way does it allow the brain and the body to go through the stages of deep sleep and dream sleep (REM), which are essential for the body’s recovery and brain function. But if the sleep is too short or fragmented, the body enters a state of ongoing physiological load, and the effects begin to accumulate.
Here are some of the things that happen in the body when sleep is not sufficient:
1. Damage to concentration and alertness: The first effect of lack of sleep is on the brain, of course. Already after one night of short sleep it is possible to feel a decline in the ability to concentrate and also a slowdown in reaction time. Studies in the field of sleep medicine have found that lack of sleep particularly harms what is called “sustained attention”, meaning our ability to remain focused on a task over time. This is why fatigue is associated with more mistakes at work, in learning and also in driving.
2. Damage to memory and learning: Sleep is a critical part of the process of forming memory. During sleep the brain “organizes” new information and transfers it from short-term memory to longer storage. When we sleep little, this process is impaired. Studies in the field of psychology have shown that lack of sleep before learning or after it may harm the ability to remember new information. In other words – the tired brain also absorbs less information and also retains it less well.
3. Increase in calorie consumption: When we sleep less, we eat more. This is one of the most consistent findings in sleep research. People who sleep little consume hundreds of additional calories the next day, mainly from snacks and especially in the evening and night hours. The reason for this is also fatigue but also hormonal changes that increase the feeling of hunger.
5. More craving for sweets and carbohydrates: Tired people tend to choose more foods rich in sugar and fat. The reason is related both to the brain but also to metabolism and the need for something stimulating. Subconsciously, the brain looks for a fast source of energy, and sugar provides available glucose that is absorbed very quickly. This is one of the reasons that during periods of fatigue or stress we are drawn specifically to chocolate, cookies or snacks.
6. Decrease in insulin sensitivity: Sleep studies have also found an effect of fatigue on sugar metabolism. It was found that even one week of short sleep significantly reduced the body’s sensitivity to insulin. When the cells are less sensitive to insulin, the body has difficulty regulating blood sugar levels, just like in prediabetes.
7. Stronger stress response: Lack of sleep and stress affect each other in both directions. Stress harms sleep, but short sleep also increases the body’s response to stress. People who sleep less report more tension, irritability and difficulty coping with stressful situations. In addition, lack of sleep also affects the regulation of cortisol, the main stress hormone in the body.
8. Tendency for abdominal fat accumulation: Lack of sleep not only affects how much we eat but also where the body stores fat. Short sleep over only two weeks (!) led to an increase in calorie consumption and weight gain – mainly an increase in abdominal fat.
9. Less physical activity and impaired muscle recovery: The effect of fatigue on physical activity is double: We will both perform less well in the activity itself, build less muscle, and the body also recovers less well: Studies have shown that lack of sleep reduces the rate of muscle protein synthesis, and lowers the level of anabolic hormones such as testosterone that are responsible for muscle building.
The bottom line: Even if it is not always possible to control the number of hours we sleep, it is important at least to try to maintain quality nutrition and avoid additional unnecessary load on the body. And if you have the opportunity – try a short sleep in the middle of the day, sometimes even one additional hour of sleep can make a big difference.