What Really Happens When You Don't Eat for 72 Hours with Dr. Mindy Pelz

What actually happens inside your body when you don't eat for 72 hours? Fasting for three days has become one of the most talked-about healing tools — but it's also one of the most misunderstood. Some people believe it's dangerous. Others think it's a quick fix. The truth lives somewhere in between. In this solo episode, I walk you step-by-step through what happens in the body during a 72-hour fast, from blood sugar shifts and ketone production to autophagy, inflammation reduction, immune system renewal, and brain healing. This episode is designed to educate, not pressure. We'll talk about who should and should not attempt a longer fast, why preparation matters, how women should approach fasting differently than men, and how to use fasting as a powerful reset. This episode also serves as a foundational resource for our upcoming FREE 3-Day Water Fast with Hay House, starting January 5, 2026. Save your spot here: https://bit.ly/waterfast2026 To view full show notes, resources mentioned, discount codes, transcripts, and more, visit https://drmindypelz.com/ep320/ https://drmindypelz.com/ep319/ Check out our community membership at https://resetacademy.drmindypelz.com Please note our medical disclaimer.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:02Mindy Pelz?

  What happens if you don't eat for 72 hours? Now, if you are new to my channel or my podcast, that probably wouldn't shock you, but I can tell you, I've had enough conversations with people to think that they would literally die if they didn't eat for 72 hours. And so I'm going to share with you all the science behind why you actually won't die. You'll actually move your body into a reparative state, one in which you thrive. And I can promise you, as somebody who's done many 72-hour fasts, it is really an incredible experience.

• 0:46Mindy Pelz?

  But let's dive into the research so you can understand exactly if it feels right for you. Welcome to the Resetter Podcast. This podcast is all about empowering you to believe in yourself again. If you have a passion for learning, if you're looking to be in control of your health and take your power back, this is the podcast for you.

• 1:15Mindy Pelz?

  So there, when you think about fasting, I always say this, I'm going to continue to say this, that we have two metabolisms. One, we activate when we eat, and one, we activate when we fast. So you've got to go about 12 hours for your body to switch from the eating metabolism to the fasting metabolism. And the eating metabolism, I call a sugar burner system. And the fasting metabolism, I call the fat burner system. So when we switch over into the fasting fat burner system,

• 1:56Mindy Pelz?

  What ends up happening is you turn on switches like healing switches in your body. So think of it like it's like it's a good stress. It's a small, little, what we call formatic stressor that activates all these cellular processes in your body that you can't activate with food. You can't even have to be with medication. You can't activate with a supplement. You can only activate it by going without food. And these switches are miraculous. I'm going to go through them here in a moment. Now, if you are new to fasting, I just want to point out that we have a beginner's guide.

• 2:39Mindy Pelz?

  So you can look at the link in the description or the show notes, depending on where you're consuming this information, and know that there's a beginner's guide to fasting. And it'll kind of get you up and going so you know how to get yourself into these 72-hour states. So let's look at this. It's going to be a bit hour by hour, but 72 hours is a long time. So if I gave you every hour, this video would be incredibly long. So I'm going to chunk it down. The first chunk is zero to 24 hours without food. I want you to think mental clarity, gut repair, and decreased inflammation.

• 3:23Mindy Pelz?

  So if you're looking for better mental clarity, you're looking to repair your gut without supplements, and you're looking to decrease inflammation, keep this fat-burning fasting window to zero to 24 hours. There's a recent review, 2024 in Nutrition Review, found that fasting's anti-inflammatory benefits kick in within the zero to 24 hours. The researchers analyzed from 23 studies and found that going at least 14 hours, this isn't that long, without food suppresses inflammatory activity across your whole body,

• 4:06Mindy Pelz?

  which can also be great for muscle recovery, joint, joint pain, and mental clarity.

• 4:13Mindy Pelz?

  You also at this zero to 24 hours, you start to burn through stored sugar and your body will shift over into ketosis. So when you're over in ketosis, you're burning fat for energy and this ketone goes up into the brain and it supercharges your brain. I remember this is I'm doing this video in March right now, March of 2025, and the last three day water fast I did is the beginning of the new year of this year. And on the third day, I was talking to a good friend of mine and she was like, did you drink too much coffee this morning? What's going on with you? And I was like, no, I'm on the third day of a fast.

• 4:55Mindy Pelz?

  And I was so mentally clear, I was so energized and it's really because of these ketones. You have two fuel sources that you need to think about to energize your brain. One is glucose, you get that through food and the other one is ketones. So you start to make these ketones in this first 24 hours. So be aware of that. The other piece that I really want to point out is that you will start to repair your gut around the 24 hour mark. You will stimulate gut intestinal stem cells.

• 5:34Mindy Pelz?

  So all of a sudden, we see the digestive system reorganizing itself, repairing itself so it can be a better gut for you when you introduce food back in. That's how brilliantly you were designed, by the way. Second phase or second chunk here is 24 to 48 hours. So this is day two. Day one, we're getting ketones, we're repairing the gut, we're lowering inflammation, we're getting all that mental clarity. Now day two hits and we're at day 25 through 48 hours and we are seeing hunger suppression that might surprise you, deep ketosis and a stabilizing of your blood sugar.

• 6:18Mindy Pelz?

  So on the second day of a water fast without food, what ends up happening is your, your whole body is like, okay, we need to keep the system functioning well. We gotta kill the hunger. We've got to make more ketones so we can energize this person to go find food. And we need to stabilize this blood sugar so we can survive in without food for a little longer. There was a 2024 study that found a 36 hour fast suppresses hunger and kickstarts weight loss and it quadruples ketone levels.

• 7:00Mindy Pelz?

  Okay, this is really important for those of you that want to lose weight. I have mentioned this on a bazillion podcasts and and videos, but I really, I just want, for those of you that are stuck losing weight, I really want you to think about this. Sometimes these longer fasts are what is needed to kick the body into weight loss mode. Weight loss is a mode. It is something you activate. And what the study found that at 36 hours, you start to see more weight loss and you see more ketones. So I've had this experience with patients over and over and over again, where we put

• 7:45Mindy Pelz?

  them in the smaller fasts and then all of a sudden they were like, well, I'm getting good results, but I'm still not losing weight. And then we we dose in these 36 hour fasts. I'll do one, maybe a couple of months later, I'll do another one. I like put them in to jumpstart the weight loss system. It is for the most powerful tool at fasting tool I've seen work for weight loss. There also was a really interesting study, 2023 study in the frontiers in cardiovascular medicine that found a 36 hour fast dramatically improved blood lipids and a marker of heart health. So if you're having high cholesterol, high LDLs,

• 8:29Mindy Pelz?

  you may look at a longer fast as well. And then there was a review, a really interesting review. These are, these are studies that I didn't put in Fast Like a Girl. Many of them have been done after Fast Like a Girl. But if you're looking for a great manual for women, Chapter 2 is actually for both men and women, really talking about the science behind hour by hour, what happens to the body when it fasts. But this 2020 review in Diabetes Markers noted that a 36-hour fast is better than shorter fasts at stabilizing blood sugar and shifting the body into deep ketosis. Let me retract the, the journal.

• 9:13Mindy Pelz?

  It is a 2020 review in Disease Markers, not Diabetes Markers. But, and, but I don't want to retract. I'm not going to retract that it's a better than the shorter fast for stabilizing blood sugar. But those of you struggling to get into ketosis, again, just know that it might be a longer fast is needed. And then our 42 to 72-hour fast. This is our stem cells, this is our immunity, and this is our supercharged fat loss. So I hope you're watching this video while you're in one of these fasts. So if you are, put it in the comments and we'll all cheer you on. Because knowledge is, is your fuel when you fast. It really is.

• 9:57Mindy Pelz?

  So after two days, you're now on third day of fasting, you will see massive cellular changes. And there's lots of, lots of beautiful things happening. A whole immune system is being rebooted and stem cells are starting to pour into your system. Stem cells are your cells that can repair any cell in your body. Stem cells are the cells that will keep you youthful. So there's a 2014 study in Cell Stem Cell, that's a journal, found that 72 hours of fasting and the immune system stem cells increase

• 10:42Mindy Pelz?

  and essentially rejuvenate the whole immune system.

• 10:47Mindy Pelz?

  During this time of fasting, you're also going into ketosis. So there was a 2012 study in JAMA that found that staying in the ketosis, not just dipping into it, speeds up your metabolic rate, those of you that want to lose weight by 15%. Now, I will tell you, I get a lot of questions on how often should you do a fast? And this kind of fast, and I just want to say that I'm a fan of it twice a year. I do one every January and I do one every September. We do it as a community. So you can head to my website and join my email list and you'll always be notified of it

• 11:28Mindy Pelz?

  or follow me on socials. But we do that as a community and it's really fun. It's a free service that I do. And last, last January, we had over 100,000 people fasting together is worldwide. It's really fun to do in a grip. So if you're interested in diving into those, depending on when you're looking at this, we can do it in January, we can do it in September. You could do it with us. Otherwise, you can do it on your own. I also have a free Facebook group called the Resetter Collaborative, where there's a lot of great fasting experts in there that can cheer you on in a, in a 72 hour fast as well. Okay, here's my first question. I love this question because it's the one I like to debunk all the time.

• 12:10Mindy Pelz?

  Will I lose muscle if I fast too long? Okay, let's, let's go into your body for a moment. When you go into these fasted states, your body goes into, I've got to unload anything that is weighing the system down. It would be a little bit like if you were on a trek through, you know, on a hike and if you were going days and days and days and you were getting tired, you might look at your pack and say, I can't carry this pack anymore. What in here do I not need that I can let go of? So to lighten your load, that's what your body's doing in a fast.

• 12:54Mindy Pelz?

  It's like, okay, we are in a crisis mode. There has been no food coming in. We have to be stronger and we gotta let go of the dead weight. So it starts to release things that no longer serves it. One of the things it will do is go into muscle and it will look for cellular debris. These are things that are holding down muscle function or extra fat cells, toxins, extra glucose. And it will start to release all of this cellular garbage. What that might feel like to you initially is your muscles are shrinking. But in a 72 hour fast, that's not what's happening.

• 13:39Mindy Pelz?

  In a 72 hour fast, your brilliant body is just releasing what it doesn't need anymore. So it can be more efficient. If you were to do a 72 hour fast over and over and over again, like once a month, every month. Now you might find that the body is breaking muscle down because it needs to get those amino acids and the nutrients that are in muscle. But that's only if you go really extreme. And to me, extreme means three day water fast, once a month. I've seen people try to do it once a week. The only time you would want to go into those states would be if you were having a severe illness.

• 14:24Mindy Pelz?

  And in a severe illness, then yes, you know, you want to be coached through that. But typically you will not lose muscle if you are being, if you are cycling the length of your fasts. Now, the other thing is you won't lose muscle if you replenish with protein.

• 14:46Mindy Pelz?

  So make sure you're getting those amino acids in when you eat. The problem that I have seen with the people who have gotten into this muscle wasting place is that they get to a spot where they, when they eat, they don't eat enough. Cause they're not hungry. It's a byproduct. It's like, why the weight loss drugs are crazy to me. You wanna save $800 or $1,000 a month and all the side effects? Just learn how to fast because this metabolic switch, when we, when we prime it, your hunger goes away. So sometimes we have to be very intentional when we open up our eating window and make sure that we are eating enough protein.

• 15:30Mindy Pelz?

  And that way we don't lose muscle. The last thing you can do is you can bring in amino acids. I'm a friend, a fan of Perfect Aminos by Body Health. I'll leave links in here for my favorite. But you might need to drink some extra amino acid throughout your day to build muscle as well. Okay. Question number two. How should I break a long fast safely? Okay. I've done a lot of videos on this and in Fast Like a Girl, I have a whole protocol. In Eat Like a Girl, a whole protocol, including recipes of breaking your fast. So know that that's available to you. But I'll tell you here that it, you, there is a step, a stepped process. The first is you always want to do broth first.

• 16:11Mindy Pelz?

  I like bone broth because it has glycine in it and it really repairs the inner lining of the gut. But if you're a vegan, you can do, in Eat Like a Girl, I have a functional, a functional broth recipe in there that you can follow as well, as well. Not as strong as, as bone broth, but some kind of broth first is important. Okay. Second thing is then we want to bring something fermented in. So you can do a fermented yogurt. You can do, you can do kombucha if you want. You can do fermented kefir, something to bring some good sauerkraut. And you can mix that with like an avocado, something fatty and bring, bring in some of those.

• 16:53Mindy Pelz?

  Find a way to get some of those fermented products into your gut so that you can repopulate your gut. Again, both books have a tremendous amount of information on this. Then the third, the third step is now you want to lightly steam vegetables. Some of us don't do great with a lot of fiber. So I want to steam it so we bring the fiber down a little bit and see how your body does. If you do well there, then the fourth step is you can bring in an animal meat if you want, and you can start to bring carbohydrates in. So that's kind of the path, like, like refined carbohydrates, not the toxic ones, but like sourdough bread and things like that. So you want to step it, you want to leave about a half an hour between each step.

• 17:36Mindy Pelz?

  But this is how we avoid the boomerang effect, which is this thing where you, where you, where you boomerang back into your bad foods. We don't want that. So again, if you want more detail, check out the books. And then the third, the third question is what's the main benefit of a longer fast compared to shorter fasts? It's a really good question. I think of the shorter fasts as like maintenance. They're, they are keeping you young, they're keeping you metabolically healthy, they're making your brain sharp. So they're important to do on a fairly regular basis. But they're not a full system upgrade. A long fast is a full system upgrade.

• 18:18Mindy Pelz?

  It is like you are telling your body, I'm going to completely reboot you. It would be like turning your computer off and turning it back on. It's just a complete system upgrade. I think twice a year, we should be focused on them. Like I mentioned, definitely the stem cells will help repair other cells in the body. You get all that autophagy that really gets rid of the, the cells that don't work well for you. But you don't, you know, once a year is even fine, but twice a year is optimal. And you don't need to do it longer than that. I know a lot of people love doing it longer than that, but you don't need to do it longer than that. So, and the shorter fasts are little micro doses, like pulses of healing

• 19:03Mindy Pelz?

  that you're giving your body every day. But you're not, maybe not doing a full system upgrade.

• 19:09Mindy Pelz?

  Makes sense. So, there you go. This is why I love fasting. I hope that some of this was new. Let me know what your longest fast is. Put it in the notes. And as always, if you're in the middle of a 72-hour and you're coming to this video, know that I'm cheering you on. You've got this. But in all the research, the extended research that I've been doing recently on the aging years for women, I am more convinced than ever that these longer fasts are incredibly beneficial for the brain, the body, and the fountain of youth. So I won't say anymore. Okay. Hope that helps. Thank you so much for joining me in today's

• 19:54Mindy Pelz?

  episode. I love bringing thoughtful discussions about all things health to you. If you enjoyed it, we'd love to know about it. So please leave us a review, share it with your friends, and let me know what your biggest takeaway is.