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Welcome to brain Stuff from How Stuff Works

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Hi brain Stuff Lorn vogelbaumb here. An

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increasing number of studies are finding a

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direct connection between sleep deprivation

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and weight gain. Generally, people

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who get at least seven hours of sleep per night

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have less body fat than people who don't. There

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are, of course, other factors involved in determining

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who will become overweight and who will not like

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food and take exercise and genetics,

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but sleep is a more integral part of the process

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than most people realize. In a study

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involving nine thousand subjects between nine

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two and four, researchers

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found that people who averaged six hours of sleep

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per night were twenty seven percent more

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likely to be overweight than their seven to nine

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our counterparts, and those averaging

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five hours of sleep per night were seventy three

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percent more likely to be overweight. Many

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people who are sleep deprived don't even know

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it. Lots of us think that there's quite a bit

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of give and how much sleep a person needs to be

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healthy and well functioning, but most researchers

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disagree, putting seven hours

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as the minimum for everyone except the

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very young and the very old. Besides

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straight numbers, there are a couple ways to tell if you're

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sleep deprived, including how fast

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you fall asleep at night. Most non

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sleep deprived people take about fifteen

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minutes to fall asleep. Falling asleep

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almost instantly, along with chronic sleepiness,

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is a good indicator that you're not getting enough

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sleep. If you are sleep

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deprived, there are some obvious tie ins to

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obesity, like your sleepiness making

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physical activity less likely, but there

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are also a number of things going on in your body

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that could contribute to weight gain. In

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scientific studies, the most commonly sided

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effects of sleep deprivation are hormonal

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disturbances, specifically involving

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the hormones lepton and grellin. When

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you don't get enough sleep, your body has too

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little leptin and too much grellin. Let's

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unpack that the hormone leptin

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is intricately involved in the regulation of appetite,

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metabolism and calorie burning.

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It's the chemical that tells your brain when you're full,

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when it should start burning up calories, and by

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extension, when it should create energy for your

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body to use. It triggers

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a series of messages and responses that starts

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in the hypothalamus and ends in the thyroid.

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Gland. The thyroid gland controls

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the way your body stores and uses energy.

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During sleep, leptin levels increase,

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telling your brain you have plenty of energy for

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the time being and that there's no need to trigger

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the feeling of hunger or the burning of calories.

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When you don't get enough sleep, you end up with

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two little leptin in your body, which, through

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a series of steps, makes your brain think

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you don't have enough energy for your needs.

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So your brain tells you you're hungry even though

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you don't actually need food at that time, and

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it takes steps to store the calories you eat

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as fat so you'll have enough energy the next

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time you need it. The decrease in leptin

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brought on by sleep deprivation can result

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in a constant feeling of hunger and

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a general slow down of your metabolism.

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The other hormone found to be related to sleep

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and wait is grellan. The purpose

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of grellin is basically the exact opposite

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of lept in. It tells your brain when you

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need to eat, when it should stop burning

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calories, and when it should store energy

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as fat. During sleep, levels

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of grellan decrease because sleep

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requires far less energy than being awake.

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People who don't sleep enough end up with too much

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grellan in their system, so the body thinks

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it's hungry and it needs more calories, and

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it stops burning those calories because it thinks

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there's a shortage. Some scientists

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hypothesize that these hormonal changes

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that occur during sleep are the result of an

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evolutionary process that favored humans

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who could survive the food shortages of winters.

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Traditionally speaking, winters have long

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nights and little food, and summers have

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short nights and an abundance of food. With

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shorter nights comes less sleep, less

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leptin, and more grellin, making the body

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eat as much as possible and save those

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calories for the long winter ahead. With

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winter comes more sleep, meaning more leptin

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and less grellin, both of which tell the

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body it's time to burn those calories it's stored

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during the summer. Sleep deprivation

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has also been ound to increased levels of

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stress hormones and resistance to insulin,

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both of which can contribute to weight gain.

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Insulin resistance can also lead to type

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two diabetes. The National

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Sleep Foundation offers the following tips

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to help make sure you get enough sleep for your body

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to function optimally, try

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to aim for seven to nine hours of sleep per

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night. Increase your exercise level,

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but try not to exercise within three hours

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of your bedtime, and don't ingest

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caffeine or alcohol near your bedtime.

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Caffeine can keep you awake, and alcohol

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can disrupt the normal stages of your sleep.

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Today's episode was written by Julia Layton and

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produced by Tyler Clang and Tristan McNeil.

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For more on this and lots of other hefty topics,

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visit our home planet, how Stuff works

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dot com.