Recently, someone I met told me "Doctor, increased weight is exclusively about calories. "The more we eat, the more weight we gain." The truth is that it's not that simple. I say over and over again that calories are a way to approach the issue of increased weight, but it's not the only way. Increased weight is caused by other factors too. After all, if you look at the overweight people and the normal-weight people around you, you'll probably not notice big differences in their lifestyles. What could be the cause, besides calories? Through this channel, I've repeatedly talked about many factors that significantly affect the weight increase. Today, I'd like to talk about sleep. What I'm going to say is based on a study carried out at Mayo Clinic, USA, one of the most important hospitals and research centers in the world, which has carried out many significant studies that have changed the way medicine works. The study was published in the respected Chest Journal and, like every study that I mention, you can find it in the description. The study was rather simple. The participants were randomly divided in two groups. The participants of the first group were requested to sleep five hours a day for eight days, while those of the second group would sleep eight hours. The researchers recorded the calories that the participants consumed. The participants had been given no advice on the consumption of food. Namely, they were allowed to consume as much food as they wanted. After eight days, both groups, namely both the group that had been sleep deprived and the group that had slept normally, were allowed to consume as much food as they needed. The researchers recorded the calories that the participants consumed. It was found that the participants that had been sleep deprived for eight days consumed 677 more calories per day than the group that had slept normally. On the days after sleep deprivation, the group that had been sleep deprived consumed 559 additional calories per day, while the group that had slept normally consumed 118 fewer calories than the calories they consumed before the study started. This led to a positive balance of 677 more calories per day for the days after sleep deprivation. Therefore, being aware that sleep may significantly affect the amount of food we eat, when we just say that increased weight has to do with how much you eat and how many calories you burn, it is an oversimplification of a really complicated problem, which has to be dealt with holistically. Saying "Your problem is that you eat much and you don't exercise enough" is at least unfair. But it's not only unfair. Since I've dedicated a large part of my professional life to helping people regulate their weight, I understand that the person saying this does not have much knowledge in this scientific field. We've seen how sleep deprivation significantly affects the consumption of food and, by extension, it leads to weight increase. Of course, this is not the only thing affected by sleep, because we know that it leads to a series of other problems and it even affects how many years we will live. If you'd like to know how many years you will live in relation to the hours you sleep, I recommend watching the video on my right. Thank you very much!