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Speaker 1: Welcome to brain Stuff from How Stuff Works Hi brain

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Speaker 1: Stuff Lorn vogelbaumb here. An increasing number of studies are

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Speaker 1: finding a direct connection between sleep deprivation and weight gain. Generally,

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Speaker 1: people who get at least seven hours of sleep per

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Speaker 1: night have less body fat than people who don't. There are,

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Speaker 1: of course, other factors involved in determining who will become

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Speaker 1: overweight and who will not like food and take exercise

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Speaker 1: and genetics, but sleep is a more integral part of

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Speaker 1: the process than most people realize. In a study involving

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Speaker 1: nine thousand subjects between nine two and four, researchers found

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Speaker 1: that people who averaged six hours of sleep per night

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Speaker 1: were twenty seven percent more likely to be overweight than

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Speaker 1: their seven to nine our counterparts, and those averaging five

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Speaker 1: hours of sleep per night were seventy three percent more

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Speaker 1: likely to be overweight. Many people who are sleep deprived

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Speaker 1: don't even know it. Lots of us think that there's

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Speaker 1: quite a bit of give and how much sleep a

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Speaker 1: person needs to be healthy and well functioning, but most

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Speaker 1: researchers disagree, putting seven hours as the minimum for everyone

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Speaker 1: except the very young and the very old. Besides straight numbers,

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Speaker 1: there are a couple ways to tell if you're sleep deprived,

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Speaker 1: including how fast you fall asleep at night. Most non

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Speaker 1: sleep deprived people take about fifteen minutes to fall asleep.

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Speaker 1: Falling asleep almost instantly, along with chronic sleepiness, is a

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Speaker 1: good indicator that you're not getting enough sleep. If you

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Speaker 1: are sleep deprived, there are some obvious tie ins to obesity,

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Speaker 1: like your sleepiness making physical activity less likely, but there

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Speaker 1: are also a number of things going on in your

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Speaker 1: body that could contribute to weight gain. In scientific studies,

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Speaker 1: the most commonly sided effects of sleep deprivation are hormonal disturbances,

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Speaker 1: specifically involving the hormones lepton and grellin. When you don't

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Speaker 1: get enough sleep, your body has too little leptin and

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Speaker 1: too much grellin. Let's unpack that the hormone leptin is

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Speaker 1: intricately involved in the regulation of appetite, metabolism and calorie burning.

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Speaker 1: It's the chemical that tells your brain when you're full,

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Speaker 1: when it should start burning up calories, and by extension,

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Speaker 1: when it should create energy for your body to use.

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Speaker 1: It triggers a series of messages and responses that starts

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Speaker 1: in the hypothalamus and ends in the thyroid. Gland. The

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Speaker 1: thyroid gland controls the way your body stores and uses energy.

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Speaker 1: During sleep, leptin levels increase, telling your brain you have

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Speaker 1: plenty of energy for the time being and that there's

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Speaker 1: no need to trigger the feeling of hunger or the

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Speaker 1: burning of calories. When you don't get enough sleep, you

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Speaker 1: end up with two little leptin in your body, which,

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Speaker 1: through a series of steps, makes your brain think you

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Speaker 1: don't have enough energy for your needs. So your brain

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Speaker 1: tells you you're hungry even though you don't actually need

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Speaker 1: food at that time, and it takes steps to store

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Speaker 1: the calories you eat as fat so you'll have enough

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Speaker 1: energy the next time you need it. The decrease in

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Speaker 1: leptin brought on by sleep deprivation can result in a

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Speaker 1: constant feeling of hunger and a general slow down of

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Speaker 1: your metabolism. The other hormone found to be related to

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Speaker 1: sleep and wait is grellan. The purpose of grellin is

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Speaker 1: basically the exact opposite of lept in. It tells your

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Speaker 1: brain when you need to eat, when it should stop

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Speaker 1: burning calories, and when it should store energy as fat.

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Speaker 1: During sleep, levels of grellan decrease because sleep requires far

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Speaker 1: less energy than being awake. People who don't sleep enough

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Speaker 1: end up with too much grellan in their system, so

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Speaker 1: the body thinks it's hungry and it needs more calories,

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Speaker 1: and it stops burning those calories because it thinks there's

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Speaker 1: a shortage. Some scientists hypothesize that these hormonal changes that

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Speaker 1: occur during sleep are the result of an evolutionary process

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Speaker 1: that favored humans who could survive the food shortages of winters.

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Speaker 1: Traditionally speaking, winters have long nights and little food, and

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Speaker 1: summers have short nights and an abundance of food. With

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Speaker 1: shorter nights comes less sleep, less leptin, and more grellin,

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Speaker 1: making the body eat as much as possible and save

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Speaker 1: those calories for the long winter ahead. With winter comes

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Speaker 1: more sleep, meaning more leptin and less grellin, both of

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Speaker 1: which tell the body it's time to burn those calories

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Speaker 1: it's stored during the summer. Sleep deprivation has also been

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Speaker 1: ound to increased levels of stress hormones and resistance to insulin,

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Speaker 1: both of which can contribute to weight gain. Insulin resistance

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Speaker 1: can also lead to type two diabetes. The National Sleep

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Speaker 1: Foundation offers the following tips to help make sure you

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Speaker 1: get enough sleep for your body to function optimally, try

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Speaker 1: to aim for seven to nine hours of sleep per night.

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Speaker 1: Increase your exercise level, but try not to exercise within

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Speaker 1: three hours of your bedtime, and don't ingest caffeine or

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Speaker 1: alcohol near your bedtime. Caffeine can keep you awake, and

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Speaker 1: alcohol can disrupt the normal stages of your sleep. Today's

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Speaker 1: episode was written by Julia Layton and produced by Tyler

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Speaker 1: Clang and Tristan McNeil. For more on this and lots

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Speaker 1: of other hefty topics, visit our home planet, how Stuff

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Speaker 1: works dot com.