Ever Wonder What Happens To Your Body When You Fast?

Rajiv Narayan Curated by

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Lots of folks do it, but what does it do to their bodies?

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Some religious groups require followers to fast for many hours a day, and continue that

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fast for days or weeks! Isn't not eating for 16 hours a day every day dangerous?

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Bom dia earthlings, thanks for stopping by DNews, I'm Trace. The Holy Month of Ramadan

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is wrapping up this week, and those Muslims who have been fasting for 15 hours a day or

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more will be able to enjoy food anytime again. It's not just Muslims who fast, Christians,

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Jews, Confucians, Hindus and other religions have followed the practice for 1000s of years.

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Non-religious folks fast too, usually for medical or dietary reasons. For some people,

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the idea of abstaining from food while the sun is in the sky is unfathomable, and they

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might feel that's it's unsafe! So science is here to demystify some fasting myths.

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A person is considered to be "fasting" if they've abstained from a meal for 8-12 hours,

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so if you think about it, most people fast every night -- and BREAK their fast in the

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morning. That's where the term BREAK-FAST came from. Fasting is a completely normal

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part of being an animal on the planet earth. Many organisms eat only once a day or less,

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especially those eating high-calorie foods like meats. Cold-blooded carnivores, like

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snakes, can go DAYS between meals, warm blooded carnivores, like wolves or coyotes, hunt daily.

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Like the coyote, humans are built to be able to fast for a short period. A day or so isn't

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going to hurt you and some studies have shown short-term fasts can extend lifespan, boost

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immunity and mental function, and so on. We did a whole video about that last Ramadan.

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A study published last month in Cell Stem Cell found that fasting two to four days at

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a time can cause a reduction in white blood cells, which is actually a GOOD thing. See,

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the cells that are killed off are the older or damaged immune cells, and when the body

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rebounds, it uses stem cells to create brand new, healthy ones.

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Long-term fasting, on the other hand, is a whole other beast. When humans fast, our bodies

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go through a very predictable schedule. Our bodies are great at squirreling away energy

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in the forms of fats and sugars. But, like coyotes, ideally, we'd eat every day or so

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to replenish those reserves. After 24-48 hours of fasting, the glycogen reserves stored in

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our liver and muscles -- basically carbohydrates -- are empty. After two days, the body's figured

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out that it needs to feed on itself, and will begin breaking down muscle and fat tissues.

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Obviously, water is important too. 72 hours without water is dangerous, so while straight

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food fasting isn't so bad for you in this short a burst, 72 hours is the beginning of

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medical dehydration. So drink water, no matter what.

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Some of you might already be Yahoo-ing to get the lowdown on a fasting diet, but the

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problem is, we don't REALLY work that way. When you fast, you lose a few pounds right

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away, but it's mainly liquid weight, and it will be replaced as soon as you eat again.

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Which is another thing, Researchers at Cornell asked college students to fast for 18 hours,

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and then offered them a buffet-style meal (not unlike Iftar, or community meals after

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sundown during Ramadan). THe most popular foods were those that were high in calories,

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carbs and starches, because our cells don't know if we're EVER GOING TO EAT AGAIN! Therefore,

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they turn on the cravings for carbs and fats which might fend off long-term starvation.

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But that's silly, you know you're going to eat again! Don't listen to your reptilian

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brain! Ideally, a human coming off of a fast would eat vegetables and fruits. Lean meats

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and a few carbs can be part of the meal, but not a big part.

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Ultimately, fasting puts stress on the systems of your body, but low-level stress isn't going

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to hurt you, and it might build up the systems -- similar to how exercise stress builds muscles.

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Fasting isn't dangerous or deadly, as long as it's done properly and in partnership with

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a healthy diet and exercise.

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If you decide to fast, let us know why and how you've done it! We're curious.

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You can fill us in on your journey in the comments, or send us a tweet at-DNews or me

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at-TraceDominguez. Speaking of journeys, if you want to know how MSL Curiosity got to

4:05

Mars, and what the heck it's doing up there come to our SpaceOut on July 30th at 4pm Pacific

4:10

Time! We're getting experts from NASA JPL who actually work with the rover on Mars every

4:15

sol -- that's Martian for Day! See you're learning already! Get over there and RSVP.

4:20

Thanks for watching DNews! and please subscribe

There may be small errors in this transcript.
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Put together by Trace Dominguez and his folks at DNews.

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