72 Hour Fast: No Food for 3 Days?!

I MADE IT! 72 hours eating zero food and drinking only water. Who? How? Why? What? I will cover all of these and your most commonly asked questions below!

Why do a 72 hour fast?

I had two main reasons for wanting to do a 72 hour fast.

  1. Autophagy
  2. Mental Challenge/ Mental Awareness About Eating

Let’s cover autophagy first. Autophagy is directly translated as “self-eating” or “self-digesting”. It the process of your body getting rid of its own damaged cells in a clearing out process of sorts.

When your body is not given food it still needs fuel, so it looks to other things. It turns to fat to produce ketone bodies for energy and also turns to its own cells, cellular components and tissues for energy. The awesome thing about this is that it doesn’t turn to healthy cells (in the span of 72 hours), it gets rid of the things that are no longer functioning properly.

Read more about autophagy here. But basically autophagy could lead to decreases cancer risk by getting rid of these cells/parts before they go rogue. Here are some other health benefits of prolonged fasting:

  • Decreased blood pressure
  • Decreased cholesterol
  • Increased control of blood sugar levels
  • Decreased inflammation
  • Increased brain cell growth

My other reason for wanting to embark on a 72 hour fast had nothing to do with physical benefits and all to do with mental benefits. I’ve always loved challenging my body in a way that gives me an adrenaline rush. Doing a bodybuilding competition was way out of my comfort zone and required a lot of mental toughness. Doing a powerlifting competition required discipline. Going skydiving promotes a huge sense of panic/adrenaline/awesomeness. Doing 24 hour fasts showed me that I enjoyed the feeling of making my body (but mostly my mind) uncomfortable. Although a lot of those activities I just listed involve the body, they involve the mind even more.

I have some performance goals with my lifting right now, but I also really missed the feeling of truly challenging myself. Going on a 72 hour fast sounded like a great way to complete a mental challenge and get physical benefits as well.

Who should do a 72 hour fast?

Short answer: Anyone how is in good health (proper nutrition, exercise, sleep and stress level) and has completed at least one 24 or 48 hour fast before. If you are not already eating good foods in the proper amounts and exercising, develop those behaviors first because they will get you far more benefit than a fast would at this point.

Longer answer: You also want to make sure you are doing a fast for the right reasons. If you have an eating disorder or a poor relationship with food, don’t do a fast. How you do you know if you have a poor relationship with food? If you cannot definitely answer no, then maybe work on things a bit.

If you are only wanting to do a fast for quick weight loss, DON’T DO IT. Yes, you will lose weight in a 72 hour fast. Yes, a PORTION of it will be from fat. But most of the weight will be water weight and from not consuming any food.

If you have read the science behind autophagy, often suffer from inflammation, or want to embark on a mental challenge, then YOU can check with your doctor to see if this is a healthy idea for you.

How do I do a fast?

I just want to preface again that before doing a 72 hour fast, I would have at least a few 24 hour fasts under your belt. Also, some people just seem to have a better time fasting than others. All of my 24 hour fasts were relatively easy, but I’ve known people who cannot make it through a 24 hour fast and really don’t need to. Not everyone needs to or should fast.

Now how to fast. The simplest answer is: only drink water. Dr. Rhonda Patrick is a great wealth of knowledge on fasting and whether or not you should consume other liquids while fasting. The science right now doesn’t really know how beverages like coffee, tea or drinks like La Croix affect autophagy. So the answer for now is, just drink water. Personally, if I am going through the trouble of not eating for 3 days I don’t want a cup of coffee to keep me from getting all the autophagy benefits that I can. Going without coffee has also been a big part of my struggle, so yay more mental benefits!

I starting my fast just before 3 PM on a Monday. So got to break my fast at 3 PM on Thursday. I’ve started all my 24 hour fasts around 6-7 PM, but starting my 72 hour fast a few hours earlier was CRUCIAL. Here’s a quick rundown of how it went:

  • Monday: Because I normally eat a high carb, lower fat diet I increased my fat and lowered my carbs at breakfast and lunch. Then I had a nice serving of gelato right before 3 o’clock. I was out of town, but if I was at home I would have tried to have a slightly more nutritious, fat-dense snack like avocado instead of gelato, but oh well.
  • Tuesday: Luckily I had eaten enough Monday to sleep well without being hungry and woke up feeling good on Tuesday. Work kept me pretty busy until dinner time, and then I noticed it was more that I WANTED to cook and eat dinner with my husband, but I wasn’t really starving or that hungry. However as the night got later and I watched an episode of MasterChef, I found myself getting hungry. It was quite difficult to go to sleep and I kept waking up hot, liking due from my metabolism increasing because usually I’m quite cold at night.
  • Wednesday: I woke up tired and with low energy, something I think coffee would have help solve A LOT. But alas, only water and I made my way to work, ran some errands, took a short nap and then finally started to feel a little more energy around 4 PM. Honestly, my energy was pretty low all day until 4. Then I quite suddenly felt a little surge of energy and much better! Going to sleep was much easier than Tuesday; I went to bed very cold and woke up very warm.
  • Thursday Pre-Breaking Fast: Waking up this morning meant only about 8 hours left! I definitely felt hungry and a little weak/low energy, but I knowing work would distract me and I was so close to the end got my through. I felt the best at the very end of my fast energy-wise.
  • Thursday Post-Breaking Fast: I was surprised at how good I felt right before ending the fast. I feel so accomplished and even though green juice and bone broth aren’t my favorite foods, it was so nice to have a fuel source entering my body. Then I add a banana with almond butter that tasted amazing. I plan to have eggs and oatmeal for dinner to keep it simple.


That sums up my 72 hour fast! Let me know if you have any questions!


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