What Happens To Your Body When You Fast?


Some religious groups require followers to
fast for many hours a day, and continue that fast for days or weeks! Isn’t not eating for
16 hours a day every day dangerous? Bom dia earthlings, thanks for stopping by
DNews, I’m Trace. The Holy Month of Ramadan is wrapping up this week, and those Muslims
who have been fasting for 15 hours a day or more will be able to enjoy food anytime again.
It’s not just Muslims who fast, Christians, Jews, Confucians, Hindus and other religions
have followed the practice for 1000s of years. Non-religious folks fast too, usually for
medical or dietary reasons. For some people, the idea of abstaining from food while the
sun is in the sky is unfathomable, and they might feel that’s it’s unsafe! So science
is here to demystify some fasting myths. A person is considered to be “fasting” if
they’ve abstained from a meal for 8-12 hours, so if you think about it, most people fast
every night — and BREAK their fast in the morning. That’s where the term BREAK-FAST
came from. Fasting is a completely normal part of being an animal on the planet earth.
Many organisms eat only once a day or less, especially those eating high-calorie foods
like meats. Cold-blooded carnivores, like snakes, can go DAYS between meals, warm blooded
carnivores, like wolves or coyotes, hunt daily. Like the coyote, humans are built to be able
to fast for a short period. A day or so isn’t going to hurt you and some studies have shown
short-term fasts can extend lifespan, boost immunity and mental function, and so on. We
did a whole video about that last Ramadan. A study published last month in Cell Stem
Cell found that fasting two to four days at a time can cause a reduction in white blood
cells, which is actually a GOOD thing. See, the cells that are killed off are the older
or damaged immune cells, and when the body rebounds, it uses stem cells to create brand
new, healthy ones. Long-term fasting, on the other hand, is a
whole other beast. When humans fast, our bodies go through a very predictable schedule. Our
bodies are great at squirreling away energy in the forms of fats and sugars. But, like
coyotes, ideally, we’d eat every day or so to replenish those reserves. After 24-48 hours
of fasting, the glycogen reserves stored in our liver and muscles — basically carbohydrates
— are empty. After two days, the body’s figured out that it needs to feed on itself, and will
begin breaking down muscle and fat tissues. Obviously, water is important too. 72 hours
without water is dangerous, so while straight food fasting isn’t so bad for you in this
short a burst, 72 hours is the beginning of medical dehydration. So drink water, no matter
what. Some of you might already be Yahoo-ing to
get the lowdown on a fasting diet, but the problem is, we don’t REALLY work that way.
When you fast, you lose a few pounds right away, but it’s mainly liquid weight, and it
will be replaced as soon as you eat again. Which is another thing, Researchers at Cornell
asked college students to fast for 18 hours, and then offered them a buffet-style meal
(not unlike Iftar, or community meals after sundown during Ramadan). THe most popular
foods were those that were high in calories, carbs and starches, because our cells don’t
know if we’re EVER GOING TO EAT AGAIN! Therefore, they turn on the cravings for carbs and fats
which might fend off long-term starvation. But that’s silly, you know you’re going to
eat again! Don’t listen to your reptilian brain! Ideally, a human coming off of a fast
would eat vegetables and fruits. Lean meats and a few carbs can be part of the meal, but
not a big part. Ultimately, fasting puts stress on the systems
of your body, but low-level stress isn’t going to hurt you, and it might build up the systems
— similar to how exercise stress builds muscles. Fasting isn’t dangerous or deadly, as long
as it’s done properly and in partnership with a healthy diet and exercise. If you decide to fast, let us know why and
how you’ve done it! We’re curious. You can fill us in on your journey in the
comments, or send us a tweet at-DNews or me at-TraceDominguez. Speaking of journeys, if
you want to know how MSL Curiosity got to Mars, and what the heck it’s doing up there
come to our SpaceOut on July 30th at 4pm Pacific Time! We’re getting experts from NASA JPL
who actually work with the rover on Mars every sol — that’s Martian for Day! See you’re
learning already! Get over there and RSVP. Thanks for watching DNews! and please subscribe.[a]

100 Replies to “What Happens To Your Body When You Fast?”

  1. I had a really bad hedache.. I fasted within 2 days and walked for an hour in the morning for those 2 days. hhh idk if its worth it. Headaches are not fun ; – ;

  2. Where i live muslims eat during designated times at night during spring and early winter/late autum because the sun doesnt set

  3. I fast because i can't afford food and i keep spending money on things i dont need. also im too lazy to get food stamps.

  4. i just did a 72 hour fast, and am now doing alternate day fasting. Its for weight loss and self discipline.

  5. I'm on my second day of pure fasting, drinking plenty of water and a little green tea. I did fast for a day previously, but broke the fast the day after because of a community grill party, that I ended with eating an avocado and Sharon Fruit. I was quite overweight, did loose a couple of Kilos with being a little more active and mindful with my food, and then decided to evaluate my life, becoming mindful of many of my addictions. Food was one of them that was out of control and needed to be managed. I looked at a couple of Video's "What I have Learned" suggesting full fasting wasn't so dangerous, as our bodies could start running on Fats and proteins instead of sugars. Over generalization, I know better, but am limited for space and your attention. Trying to reach Keitogenesis, my body has experienced high energy, and my mind is noticeably clearer. I'm going to see my GP to see what supplements I should be looking to include into my system, while I'm on the cleanse. But apart from occasionally feeling hungry (especially if food is in my vicinity), I feel better than ever.

  6. went on a fast during a very difficult period. only ate lunch, usually the cheapest veggies i can find in the flea market. i consider myself lucky if i got some fish. been like that for a month, lost more than 6kgs.

  7. I'm going on a fast tomorrow for religious reasons and to loose a bit of weight, I'm going to do it for 9 days but I plan to work out during my fasting session and go to sleep earlier and take naps during the afternoon.

  8. Hi I love intermitting fasting I wake up ready too get my walk on I feel so energetic I can do anything during my 18hr fast but when eat I don't feel so energetic is that normal?

  9. After 2-3 days… the body uses ketones, and that is what fat is made up of…
    So u'll loose real fucking fat..
    improve cognition…
    amazing skin in just 3-4 days…
    and last but not the least 17 hours of free lonnnnnnnnnggggggggggggg Days

  10. I have been fasting for a year now i find it much better than doing a regular diet. I do 20:4 fasting and usually work out when i get the time 4 times a week.

  11. When my mom was vegan, she fasted for a whole week. No food, no water. I was little at the time and when I layed my head on her stomach, I could hear her heart beating. That sounds weird now that I wrote it.

  12. 4:01 I was digging the channel… until this point. We've never even landed on the moon. Nothing is at Mars except Science Fiction. The Earth is flat, or haven't you been let in on that little secret…

  13. I liked to fast as a kid because I wasn't hungry as much. I just wanted to eat when I wanted to. Sometimes that'll be once a day, (24 hour fast) I just randomly decided to do one today. I'm on my 9th hour and I feel energized.

  14. I believe in fasting not only does it make weight loss speedier, but it doesn’t destroy you metabolism. And apparently there is a correlations in many organism between calorie restriction and longevity.

  15. Your body does not break down muscle during a long fast if you carry excess weight. Your body is smart enough to use stored energy. It would only start eating muscle if you'd drop below the 6% body fat you require to live.

  16. Why do you think you lose your appetite when you are really ill, because your body wants to use all its energy for healing instead of using it for digestion

  17. Fasting doesn't break down muscle. Why break down muscle when there's fat stores? The body isn't stupid, it knows how to run on ketones.

  18. I’ve been on a 10 day fast. I lost like 15 pounds. I’ve been fasting on and off for a year now and I lost 80 pounds along with exercising and eating in smaller portions. It’s a good way to get your body to eat less bc your stomach shrinks I think

  19. I have been fasting on the average 19 hours everyday for the past nearly four years. I will never go back to the NWO 3 meals. I eat just one meal per day. Even my hair is happy. From ugly graying white hair to nearly dark black. I am over 50 and I feel very flattered when young girls approach me obviously having no idea about my age.I suddenly realise that I am looking younger doing nothing except IF.

  20. In our area, Women Fast every Monday… for Hindu religious reasons… its believed that Fasting every Monday will make them Pretty (or Younger looking..! ) and will get a good husband and a healthy married life… i fasts on Sunday ( & sleep all day 😉 )…
    Fasting Rules : Breakfast is a must, can have water, but no food all day.. for dinner eat Vegetables/Fruits…

  21. The worst part at fasting is you're not allowed to swim in Pools and Ramadan was in summer last year, so everyone was out there in the swimming place and we were just waiting for iftar

  22. i am not taking breakfast . i am only taking lunch and dinner . i have 16 hours of gap between my dinner and next lunch .is this a good habbit ?

  23. I was thinking about the word breakfast in Spanish Desayuno (ayuno=fast) when he was explaining we break our fast in the morning and I didn’t notice that in english !! 😂😂 English is much closer for me to be a mother language than Spanish tho 😂🤦🏻‍♀️

  24. i am doing a water fast and want to see what happens to me my nigest goal is to lower my blood sugar levels and lose a few pounds.so i will keep you guys posted and see if this actually works.

  25. Long term fasting isn't necessarily dangerous in my research, and does not necessarily lead to muscle loss if you are getting proper exercise during the time and have fat reserves to sustain you.

  26. I'm doing a water fast for 72 hr as I here there can be a number of health benefits inculcating more HGH, Detox the body, make your body consume scar tissue, cancer cells. I would have done longer but with a BMI of 24 DR thinks its a bad idea to do more.

  27. PSA: DO NOT fast for more than a day when you have diabetes! I did a fast for 7 days, although I had type 2 diabetes and I ended up in hospital for a week! Because there was no more insulin in my body at all + a whole range of other things. (I just didn't know about this at the time.)

  28. I do Keto with an 20 hr fast every day and a 4 hour eating window. It helps my pain as its Antiinflamatory and healing.

  29. I started my intermittent fasting "journey" 38 days ago. I needed something simple and easy to maintain, with minimal rules. No long-term "goals" or "targets". The journey is the goal. Live a bit more healthy without throwing in the towel and never enjoying a meal again. So, I bought a treadmill 38 days ago and started an intermittent fast diet the next day. I've been wholly sedentary for over two years, working in my basement at home. I don't even walk to the car, into the store, or into a workplace. I was just sitting in my basement and… Expanding. So I had to start off slow. I think I started at half a mile & 10 minutes on the treadmill (both). Then, just stepped it up slowly. I'm 38 days in. I walked 4.5 miles this morning. I'm intentionally putting little importance on the scale, but for anyone curious, I'm down 19 pounds as of this morning. Started off my largest ever, at 248 lbs, and am at 229 as of this morning. I would say "long way to go", but I'm not thinking like that any more. Yes, I have a long way to go. Hopefully, decades. This is not a diet or a fad. This is my life. This is my existence. This is my journey. The real test will come next time I am on vacation. If I can keep up my routine while on the beach in Florida, I'll count that as a victory! Anyway, if interested, I've been blogging my experience most days. You can read more here: https://healthychay.wordpress.com/

  30. Um am 15 should i do this and will it affect me in same way as a adult or can it actually lead to death because am younger dose anyone know??😓

  31. I did a 4-day fast last week (except for electrolyte supplements) and got real fuckin sick when I tried to reintroduce food lol

  32. That Breakfast fact blew my mind. But overall you have'nt said anything clearly what happens during a fast to my body and weight changes, energy level changes. And some of your points contradict others

  33. How hard is fsting ! Please watch once .https://www.youtube.com/watch?v=3qP7dm06dLA&feature=youtu.be

  34. Part of what he is saying is true, but the other part isn’t. Everyone says you gain the weight back, and while that’s true it’s only to a certain extent. Of course because everything we eat has water we will in fact gain back water weight, but the weight you lost from the body eating away at itself is in fact fat already gone. I should know. I have fasted to get to my ideal weight and have managed to keep it off through eating properly and exercise. Anyone who doesn’t eat healthy and exercise whether fasting or not and continue to indulge in high calorie foods and sweets will gain weight regardless 💯💯

  35. Bro! You need to learn more about a subject before you make a video. I’ve done 40 days fasting and he has been the most healthier stuff I’ve done in my life. There’s a lot of stuff that you’re missing. Please do not make videos about stuff that you know nothing about.

  36. The Most Important Thing I've Learned When I tried Fasting Was How to Appreciate Food And I Realized We've all taken It For Granted

  37. I’m both a long term and intermittent faster for both spiritual and religious reasons! Really increases gratitude at the very least 🙂

  38. Wow people here are so unaware of what theyre watching considering the like/dislike ratio. This guy just told you that meat is high in calories, which is totally the opposite of the truth (1:06).

  39. I lost hope with humanity seeing these people in the comments wowing on break fast like really how long have u been on this earth 🤦🏽‍♂️

  40. I need to eat something almost every 4-5 hours that I'm awake. Even just something small or else I get light headed, cranky, disoriented, or altogether just don't feel very well. Fasting for blood work is painful..

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