Every night, after the sun goes down and your favorite show is over, you head to bed and voluntarily lose consciousness for (ideally) eight hours. When you think about it, sleeping is a strange thing to do, and yet it’s essential for survival. It allows your brain to detoxify and rejuvenate for the day ahead. It releases hormones that keep you sharp, regulates your body, and is the time that your brain converts short-term memories into long-term memories. But even with all the fascinating things that researchers know about sleep, there’s still a lot of mystery. Here are four things you never knew about sleep.

Person sleeping under white sheets with alarm clocking ticking in foreground
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The recommended eight hours of sleep takes up one-third of the day, and thus one-third of your entire life. If a person lives to be 75 years old, he or she will spend about 25 years asleep. It’s the most time-consuming thing you will do in your entire life.

Yet, more than one-third of Americans aren’t getting enough sleep every night. You might think that people who live in relaxing climates would enjoy more sleep, right? In fact, Hawaiians enjoy less sleep than anyone else in the United States. Almost half of adults living in Hawaii report getting less than seven hours of sleep every night. People living in South Dakota, however, get the most sleep of anyone in the U.S.

Sleeping can affect weight loss

Doctor pulling tape measure around patient's waist to estimate body fat levels
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Sleeping less than the recommended seven to nine hours per night can have major consequences for your waistline. Sleep regulates the hormones that control your appetite and hunger. Leptin is the hormone that makes you feel full and tells your body to use energy. If you’re trying to lose weight, leptin is your friend. When you don’t get enough sleep, leptin levels are reduced, while levels of ghrelin, a hormone that makes you feel hungry, rise.

Being low on sleep can also affect your decision-making skills. If you don’t have the energy to do physical activities, you default to sitting on the couch watching the same TV series for the sixth time. If you’re tired, there’s more of a chance that you skip cooking and order a pizza. In fact, your body becomes so desperate for energy that you start to crave foods high in fat and sugar.

Weight gain from lack of sleep can come on quickly. People gain on average about 2 pounds per week if they sleep less than five hours per night.

Women need sleep more than men

Woman sleeping peacefully on white sheets while wearing white shirt
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Compared to a one-task-at-a-time mindset, multitasking uses more parts of the brain at once, which requires more of a recharge at night. While the stereotype that women can multitask better than men has dubious scientific backing, a British researcher found that on average, women need an extra 20 minutes of sleep compared to men, and pointed to multitasking as a reason.

Unfortunately, women are also more prone to sleep disorders and are more affected by a lack of sleep. In the case of snoring, men can often be the cause of women’s missed sleep. Snoring is a sleep disorder more common in men which, of course, causes a lack of sleep for their partners.

You dream every night

Mother, baby, and dog laying on bed together and falling asleep
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Dreams occur during the most active stage of sleep, the REM cycle, which stands for "rapid eye movement." Every time you enter this stage, typically about four to six times per night, you’re dreaming. Whether or not you remember your dreams in the morning is a different story. Even though you might have six dreams every night, you will forget 95-99 percent of them.

Scientists still aren’t sure why people forget their dreams. The most compelling theory is that norepinephrine, the hormone that controls memory and attention, exists only in very low levels during sleep, which affects the creation of memories. When you wake up in the morning, you have no new memories, so it’s like nothing happened at all.