Welcome to brain Stuff from How Stuff Works Hi brain Stuff Lorn vogelbaumb here. An increasing number of studies are finding a direct connection between sleep deprivation and weight gain. Generally, people who get at least seven hours of sleep per night have less body fat than people who don't. There are, of course, other factors involved in determining who will become overweight and who will not like food and take exercise and genetics, but sleep is a more integral part of
the process than most people realize. In a study involving nine thousand subjects between nine two and four, researchers found that people who averaged six hours of sleep per night were twenty seven percent more likely to be overweight than their seven to nine our counterparts, and those averaging five hours of sleep per night were seventy three percent more likely to be overweight. Many people who are sleep deprived
don't even know it. Lots of us think that there's quite a bit of give and how much sleep a person needs to be healthy and well functioning, but most researchers disagree, putting seven hours as the minimum for everyone except the very young and the very old. Besides straight numbers, there are a couple ways to tell if you're sleep deprived, including how fast you fall asleep at night. Most non sleep deprived people take about fifteen minutes to fall asleep.
Falling asleep almost instantly, along with chronic sleepiness, is a good indicator that you're not getting enough sleep. If you are sleep deprived, there are some obvious tie ins to obesity, like your sleepiness making physical activity less likely, but there are also a number of things going on in your body that could contribute to weight gain. In scientific studies, the most commonly sided effects of sleep deprivation are hormonal disturbances,
specifically involving the hormones lepton and grellin. When you don't get enough sleep, your body has too little leptin and too much grellin. Let's unpack that the hormone leptin is intricately involved in the regulation of appetite, metabolism and calorie burning. It's the chemical that tells your brain when you're full, when it should start burning up calories, and by extension, when it should create energy for your body to use. It triggers a series of messages and responses that starts
in the hypothalamus and ends in the thyroid. Gland. The thyroid gland controls the way your body stores and uses energy. During sleep, leptin levels increase, telling your brain you have plenty of energy for the time being and that there's no need to trigger the feeling of hunger or the burning of calories. When you don't get enough sleep, you end up with two little leptin in your body, which, through a series of steps, makes your brain think you
don't have enough energy for your needs. So your brain tells you you're hungry even though you don't actually need food at that time, and it takes steps to store the calories you eat as fat so you'll have enough energy the next time you need it. The decrease in leptin brought on by sleep deprivation can result in a constant feeling of hunger and a general slow down of your metabolism. The other hormone found to be related to sleep and wait is grellan. The purpose of grellin is
basically the exact opposite of lept in. It tells your brain when you need to eat, when it should stop burning calories, and when it should store energy as fat. During sleep, levels of grellan decrease because sleep requires far less energy than being awake. People who don't sleep enough end up with too much grellan in their system, so the body thinks it's hungry and it needs more calories, and it stops burning those calories because it thinks there's
a shortage. Some scientists hypothesize that these hormonal changes that occur during sleep are the result of an evolutionary process that favored humans who could survive the food shortages of winters. Traditionally speaking, winters have long nights and little food, and summers have short nights and an abundance of food. With shorter nights comes less sleep, less leptin, and more grellin, making the body eat as much as possible and save
those calories for the long winter ahead. With winter comes more sleep, meaning more leptin and less grellin, both of which tell the body it's time to burn those calories it's stored during the summer. Sleep deprivation has also been ound to increased levels of stress hormones and resistance to insulin, both of which can contribute to weight gain. Insulin resistance
can also lead to type two diabetes. The National Sleep Foundation offers the following tips to help make sure you get enough sleep for your body to function optimally, try to aim for seven to nine hours of sleep per night. Increase your exercise level, but try not to exercise within three hours of your bedtime, and don't ingest caffeine or alcohol near your bedtime. Caffeine can keep you awake, and
alcohol can disrupt the normal stages of your sleep. Today's episode was written by Julia Layton and produced by Tyler Clang and Tristan McNeil. For more on this and lots of other hefty topics, visit our home planet, how Stuff works dot com.