How to do an extended Fast from 48 hours to 100
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As part of the Keto Mini Challenges in 2021 we decided to first do the Fat Fast by Dr. Fung’s 3 followed by an extended 48 hour fast. This blog post will focus on the extended fast . To learn more about the fast fast please check out the Fat Fast Blog Post.
The different names of long Fasts
Longer fasts go by different names:
Extended Fast
Prolongued Fast
Cleansing
Puryfiying
Detox
The version I did, also goes by Water-only Fast
And I’m sure there’s more.
How do Extended Fast work?
Extended fasts mean that for a longer period of time you won’t be consuming food. If you hear about Intermittent Fasting that means no eating for 16-18 hours of the day. Time restricted fasting is similar where you eat within a window of time. You can push beyond that though into an extended fast and fast for 24 hours, 48 hours or even 100 hours like I ended up doing.
More on benefits below. As you proceed keep in mind: This is not about cutting calories. Extended fasts will reset your body. Shift the way organs work. It is not to be taken lightly and I recommend checking with a medical professional whether this is right for you before going beyond 24 hours. Especially if you have any preexisting conditions. This is also not suitable for pregnant or breastfeeding women as well as kids under 18 or anyone who is undernourished.
After having read the ‘Complete Guide to Fasting’ by Dr Jason Fung and Jimmy Moore I also want to add that fasting is not a new concept. It’s been around since pre-historic times. The book included the following quote from Marie Antoinette:
“There is nothing new except what has been forgotten.”
Fasting just isn’t as popular as it once was but still an integral part of religious rituals and recognized as highly effective in the treatment of various health conditions including obesity and type 2 diabetes.
What you are consuming during an Extended Fast
As part of the Mini Challenges we decided to do a water based fast. Meaning we would only consume:
Water
Maybe some tea or coffee
No sweetener
Electrolytes or pink salt as we saw fit
No other supplements if not medically required
Bone Broth was optional - I opted for none
What are benefits of an Extended Fast
As mentioned above, this goes beyond cutting calories, but the lack of food does lead to weight loss. Let’s see the full list of possible benefits. I want to emphasize the ‘possible’ because every BODY is different!
Weight loss
Reduced hunger and cravings as your body moves into Ketosis thanks to the ommission of food
Get into a very deep level of Ketosis - I shared mine further down and got so deep that my measuring device could not assign a number anymore
When going beyond 48-72 hours, cell regeneration will set in. Yes, your body - when not getting food - will kinda ‘turn on itself’ to find fuel which means dead cells will be removed and replaced with new ones. This is also known as Autophagy.
Brain regrowth: Yes, sounds crazy but there have been many studies that have shown prolonged fasting to lead to regrowth of brain cells
Increase in energy: Again, sounds weird that when you stop eating you get more energy but its true. If you want to learn more, read up on Mitochondria.
Less to no inflammation: You’re going to detox and loose water weight during extended fasts which will result in less inflammation
Less stress: As your body slows down you will possibly feel a lot let stress and much calmer about daily occurences in your life. It’s like your body switches to being very selective about what to allocate energy on
Slowing down of Tumor growth: For cancer patients, extended fasts can help in slowing down the growth rate of Tumors.
Support in finding food intolerances: As you will transition out of your extended fast you will slowly reintroduce foods which will help you also uncover which you are more sensitive too than others
Break habits: If you were used to snacking or overeating on something, a prolonged fast will not only break this habit temporarily but also show you that you can live without it!
Build confidence: It is an incredible feeling to conquer your mind and fast for more than 24 hours. You might realize how you were enslaved to certain patterns and how you were overfocused on food. I know that when I saw my counter reach 100 hours I felt extremely proud - and surprised that I had been able to fast this long.
I’m sure there’s more I haven’t listed but I believe this is a great start!
How to get started with an Extended Fast
I started by doing a 3 day Fat Fast (write up here) as designed by Dr Jason Fung and as a last meal had bacon, egg, avocado, pork rinds and a Ribeye steak.
What I’ve heard from others who have tried this is to not overeat on your last meal. You do not want to go into an extended fast with an extremely heavy belly and with 2 days worth of food. Eat your regular meal. Make sure you have a good amount of Fat and Protein as well as vegetables for the vitamins. For me, I decided to add a Ribeye to my dinner which is not part of the Fat Fast but which I knew would provide me with the Vitamin B12 I would need in the coming days as I tend to have a Vitamin B12 deficiency.
When to start an Extended Fast
First, overall timing: Pick a week or days where you’re not committed to dinners with friends or drinks. EIther a time when you’re so busy that eating won’t even be on your mind or a time where you’re at home and can easily not eat. If you live with family and /or kids: I will touch on this later in the post.
Time of day: I would suggest starting after dinner and don’t make dinner too late. Why? I ate until 7pm and then started my fast. This meant that to reach 48 hours I would have been able to eat again 2 days alter after 7pm. I ended up extended though and by doing 100 hours, that meant I broke my fast at 11pm. This is an extreme example but your get the jist.
Also, sleeping time is the easiest time to fast, so starting with that is great!
Time of the week: If you are in a position to sleep in on the weekends then start your fast on a Thursday and use the Saturday and Sunday sleep ins to make it easier for you.
Set a clear goal for your Extended Fast and track
What do I mean by a clear goal? Define how many hours you want to achieve. If you have an accountability buddy or family member living with your or friend, tell them!
I - as part of the group of people I did this with - let myself be talked into 48 hours as a goal. Yes…I really did not think I could do it. I thought 36 hours was doable. Basically a day and adding a nights sleep but as you’ll see further on I was able to keep going.
I told my family I was going to be fasting for 48 hours to which my 7 year old asked whether that meant I was going to be hangry for 2 days lol I thought I would be, but again as you’ll see below. I wasn’t.
As for tracking: I thought I would not need this. Hey, I can read time after all. But as I went beyond 24 hours it was really satisfying to see that tracker tell me how many hours I had fasted.
The ‘Zero app’ was recommended to me and I have to agree that it’s very simple, easy to set up and perfect to show progress. You can also log your mood and feelings and I was very happy to see the hours go buy as I checked it.
How long should you aim to fast for?
I would recommend to add for a ‘lower’ number initially which you can always extend and work yourself up to longer fasts over time. One thing that you should ALWAYS remember: Fasting should not make you feel terrible or ill. If it does, stop and try again another time. The longest water-only fast a man did was 382 days. Only water and a multi vitamin. Commonly people aim for 4-14 days though.
What to do during the Extended Fast
This might or might not surprise you, but live life as usual. Continue to work, continue your exercise and just skip anything related to food.
I continued to log my 10,000+ steps a day. I continued to do my HIIT and Cardio workouts for the first 3 days and modified to take it slower on Day 4 and the day after I broke my fast.
What’s most important though is to drink lots of water and getting electrolytes. No need to go crazy here though. See my day by day below and how I incorporated electrolytes and salt.
Is it possible to do an Extended Fast when living with Kids, Family or Friends?
To my surprise: YES. My first 2 days my husband was around and I didn’t ‘have’ to join meal times which was great to get more time for work but then he left for the weekend and I managed day 3 and 4 solo. Including baking a chocolate cake with the kids, making them Spaghetti Carbonara and sitting with them as they are plus breakfasts and more. To my surprise, sometime between hours 36-48 I lost all interest in food. No appetite. No hunger. I didn’t feel it was hard at all to cook and bake with the kids.
How to end the Extended Fast
I’m not an expert on this as this is my first experience but I’m learning from my own mistakes already. Full write up of my days on the Fast and after the fast to follow, but generally speaking: TAKE IT SLOW!
After a 24-48 hour fast, you should be fine with a small meal. Not too fatty. Stick to protein and vegetables. Eat slow. Chew well to help your digestive system.
If you went 48-100+ hours: Take it one food at a time. Starting with e.g. broth and an easily digestible watery vegetable like cucumber. Keep portions very small. Eat very slowly. Chew a lot. Eat a bit. Take a break and see how your body reacts and then eat some more. Slowly ease your way through different foods from easily digestible to harder. Wait for dairy for Day 2. Basically eat similarly to as if you were nauseaous or had the flu. Minus the crackers if you’re Keto. No sweeteners until Day 2 or later. No alcohol.
Ok, ready for my story, stats and lessons learned? Let’s go.
I wanted to cover the Extended Fasting 101 first before moving on to how I went from believing I could do 36 hours, to 48 hours to extended to 72, 90 and finally 100 hours of fasting.
This has been such a wild ride and an experiment I don’t see myself ever forgetting.
How did the Extended Fast work for me?
Let’s start with my day by day before moving on to numbers:
Day 1 of the Extended Fast:
I started on a Wednesday evening with my last meal being Avocado as Guac’, Bacon to dip, Pork Rinds to dip and Ribeye. After 3 days of Fat Fast it felt very satisfying to have that Ribeye and I started my fast very content.
Last meal before the fast started
Ultima Electrolytes used on Day 2 and 3
I went to bed, woke up the next morning, did my HIIT workout and morning walk. I skipped lunch which I would usually have around noon. I worked instead and enjoyed the extra time to get work done.
Did my midday walk. I felt fine as I new I could easily do 24 hours. In 2020 I had done OMAD (One Meal A Day) for a while, so mentally I know that I could do it.
Prior to dinner time I joined the family for our evening walk. When dinner time rolled around, I again kept working and did not join the family. Water wise I drank about 180oz. I usually drink about 160oz, so this wasn’t unusual for me.
I decided to add a bit of Electrolytes to my water in the evening. I had a sample sachet of Lemonade Ultima and added about 1/4 of it to my water after checking ingredients and confirming it had no calories, no sweeteners. I instantly felt clearer in my head although I hadn’t even noticed I wasn’t that clear. That confirmed for me that I would need to add a bit of electrolytes. I usually don’t take supplements so I’m always a bit hesitant.
My energy levels were fine, I fell asleep better than usual. My digestion was fine as well.
Day 2 of the Extended Fast:
I woke up Friday, did my stretch workouts and was glad it wasn’t HIIT because I felt a little weak on my legs.
I decided to add a bit more Electrolytes to my water. Did the morning walk. Worked. Midday walk. Worked. By evening I sat with the family for dinner and watched them eat.
I had reached my 48 hour goal. I decided that, because I had no hunger or appetite I would add the night to my fast.
I again drank about 180oz over the day and bit by bit added the rest of the Ultima Lemonade electrolyte sachet which usually would have been for one 8oz cup.
Energy was ok but my legs felt heavy. I fell asleep fine again. Digestion was normal as well.
Day 3 of the Extended Fast:
I woke up. Did a modified HIIT workout - no burpees as I felt like the up and down might be tricky followed by almost an hour of Just Dance with the kids - felt like I was a bit behind on the beat but otherwise fine - followed by 20 minutes of Yoga.
I still felt no hunger or appetite and decided to keep going and see how it would go.
What I haven’t mentioned so far are the physical changes. By day 3 I felt like I had lost a dress size. My leggings were loose. My stomach hasn’t been this flat since I was a teenager.
I made the kids lunch - don’t remember what - watched them eat and then we went ice skating. On day 2 I had been a bit hesitant to drive around fasted as I worried my concentration might be affected but by day 3 I felt confident that while my body felt heavy, it did not impact my ability to drive or focus.
Ice skating was fun and once we were back home we baked a chocolate cake from scratch. Yep. Non-keto. It smelled amazing and I was not the least bit tempted. Nothing. Not even jealous when they licked the batter ;) After that we chilled, played games and I enjoyed not having to move too much. For dinner I made them spaghetti carbonara plus cucumber and watched them eat.
Throughout the day my water intake was consistent around 180oz and I ate Redmond Real Salt every hour or so. That really helped with clarity.
Mood-wise to all of our surprises, Mommy did not turn hangry at all. I was actually much more chill and relaxed. As by dinner (72 hours in) I still didn’t feel like eating, I decided to add another night.
Legs still felt heavy here and there. Sleep came easy. Digestion still normal.
Day 4 and Last Day of the Extended Fast:
After waking up I did my Sunday morning walk on the treadmill while reading and until I had logged my 10k steps. Rather than doing my usual pace of 6.5km / hour I did 5.5km / hour.
I planned to go until 90 hours with the fast which would have been around 1pm. As I got closer I started thinking that 100 hours would be really cool though.
That was the first time I started to feel like I needed to push myself. I was still not hungry per se but wanted to eat. To have the sensation of food in my mouth.
Snack time was easy with the kids. Dinner was a bit tougher to sit through. 100 hours brought me to 11pm and I distracted myself by listening in to lives on TikTok.
Water-wise I still was at about 180oz. Still taking Redmond Real Salt here and there. Taking it slow on the stairs in the house though. Mentally clear. Flatest belly ever with pants that fell off.
How I ended my 100 hour fast
I knew as soon as I set the 100 hour goal that although it would be easy to add an extra night I wasn’t going to do that. There was no point for me to continue endlessly. 100 hours is amazing and at that point doing 110 hours or so didn’t feel like I would get any extra benefit.
I broke my fast with a soft boiled egg and 2 oz of chicken bone broth. I ate very very slowly. Like, it took me 20 minutes to eat that. No digestive issues. Went to bed exhilirated and amazed that I had made it and slept well.
Keto Anywhere Extended Fast First Meal
Keto Anywhere Extended Fast First Meal
Transitioning out of my 100 hour fast
I would love to write that transition was super easy. A walk in the park. But it wasn’t. This was the first time I felt challenged on this fast. Yes…not during the fast, but after.
Although I usually Intermittent Fast and only eat around noon I decided to do a light breakfast. 2 soft boiled eggs (hey, the 1 had worked so well the night before) and 4 oz of chicken bone broth. I ate slowly but not as slowly as the night before.
Extended Fast Breakfast
Extended Fast - Lunch Day 1
I then went on our morning walk and on the walk I started feeling weak and had stomach cramps. We finished the walk and I went straight to the bathroom. More cramps. TMI: watery diarrhea. It was bad. After that I decided to lay down with a heat mat on my stomach for 30 minutes.
Call me crazy, but I’m a creature of habit and then decided to do my HIIT workout. Modified. No burpees or jumping jacks and jogging in place instead.
Lunch was about 2oz of chicken cooked in coconut oil ( to not reintroduce dairy yet) along with a bit of cucumber and chicken bone broth. I also had a few tiny bits of bacon we had left from the day before. Like 1/10 of a bacon strip. Eating the chicken and chewing it endlessly felt glorious. Same with the cucumber. I’m always amazed after these fasts at how much more I perceive flavors and textures.
2 hours later I was back to dealing with cramps and bathroom runs.
Also interesting was that while in the days before I easily drank tons of water, on this day I had to push myself. By dinner I was only at 80oz. Luckily the broth helped with hydration too.
Evening walk came next. Ok, but still a little shaky on the legs.
For dinner I had 5oz of chicken breast cooked in coconut oil with 2 oz of zucchini cooked with it. Also about 2 Tbsp of full fat Greek Yogurt as I read in the afternoon that many people take probiotics when re-feeding and that Greek Yogurt was a good option for that too.
Also, I’m going to be fully transparent here: In the afternoon I started craving my favorite Keto friendly chocolate from ChocZero - the Hazelnut Dark Chocolate Sea Salt Bark. I stayed strong until after dinner and then thought, hey. If my digestion is already messed up I might as well have some chocolate. If you want to order some, you get 10% off with code KETOANYWHERE through this link.
Extended Fast Dinner Day 1
Chicken Bone Broth I ate to break the fast, Found it at Aldi
Extended Fast Chicken Bone Broth Nutrition Facts
Enough story time, let’s see the Extended Fast stats
If you’ve read my other blog posts you’ll know that I’m all about the numbers. My standard is to share weight evolution, Ketones, Glucose, Glucose Ketone Index and Macros. For this one I’ll also share my Fat loss and impact on Muscle and Water as per my Renpho SmartScale.
Weight first. Incredible weight loss for me that reflects my super flat tummy. Now to see how that evolves beyond refeeding for a week. A lot of weight loss is usually water weight due to reduces inflammation which you will regain as you eat inflammatory foods again.
I also want to share the Body Fat Loss, Body Water evolution and Skeletal Muscle gain. This really shows how being in deep Ketosis will melt the fat! To get these stats, all you need is a Renpho Smart Scale that are available as low as $19. You can get 10% off with code KETOANYWHERE10 on the Renpho site or buy on Amazon.
I also measured my level of Ketosis, Glucose and the resulting Glucose Keto Index (GKI). This one was a highlight. On Day 4 my level of Ketosis was SO high that the Keto-Mojo could NOT measure it. It was literally off the charts!!
If you’re not sure how to interpret the above, do not worry. Here are some great infographics from Keto-Mojo whose measuring device I’m using:
Level of Ketosis - Yellow Line in my chart above. The higher the better
Glucose levels. Black line in my chart above. The lower the better.
Glucose Ketone Index. Grey line in my chart. The lower the better
As you can see I started already in high therapeutic Ketosis and went into the highest leve possible. 5 days of refeeding and I was still in high levels of Ketosis given that I eat a Keto and Low Carbohydrate diet.
This means throughout this experience my body was burning fat for fuel and given minimal glucose to burn for energy. The Fat loss came from the fact that during fasting my glucose and glycogen ‘storage’ was depleted giving my body no other choice than to draw energy from my fat storage.
Calories stored as Glucose = Used for immediate energy needs
Calories stored as Glycogen = For intermediate energy needs
Calories stored as Fat = For long-term energy needs
If you’re curious about your levels I highly recommend buying a Keto-Mojo Device. You can either get 15% off the Starter Kit ($44.99 to 49.99) by shopping through this link or get it on Amazon.
If you’re curious about Glucose, Glycogen, Fat and Insulin I recommend reading The Obesity Code by Dr Jason Fung.
The stats wouldn’t be complete without some insights as to my refeeding. Here are the Macros as well as the view on caloric intake:
My learnings with doing an Extended Fast
I’ve done my fair share of fasts in these past months from egg fast to dairy free to carnivore. See my blog for those write ups.
This one was different though. From having a goal of 48 hours, to thinking there was no way I’d make it past 36 hours to extending to 100 hours.
What a ride and what amazing results!
Here are my learnings in a nutshell:
Before and Starting the fast:
REMINDER: If you have any preexisting conditions or are in any way unwell, consult a medical professional before embarking on a fast
As I talked with friends about my experience I realized that I might have had an easier time easing into this because I’ve been eating a low carbohydrate diet for years + I did a Fat fast going in which meant I was already in moderate Ketosis. If you’re going from a regular diet to a fast you might experience the Keto flu and other symptoms that will make the first 2 days harder. Hydration will be key as well as salt or electrolytes.
As you set your goals think about whether this is only a food based fast for you or whether you want to detox completely. This might include avoiding lotions that might introduce toxins into your skin as well as shampoo or deodorant.
I fasted in February. The experience might be different in summer if you’re out and about. Keep that in mind as you find the perfect timing.
If you’re unsure about fasting in general, I highly recommend reading The Complete Guide To Fasting.
During the fast:
Electrolytes are crucial when you enter Day 2. No need to overdo it. Listen to your body. Take a bit and see if it helps and then do it again
Unbelievable but I lost interest in food, stopped being hungry and having appetite at the end of day 2. So give yourself time to get there and then ride the wave. Hunger generally comes in wave and if you’re lucky like me you’ll soon hit flat water
If you’re not used to drinking a lot, set yourself a timer. Drink a big glass of water right after getting up. Invest in a pretty bottle and keep it around you at all times.
You can continue to exercise. You might need to make some modifications if head up and down throws you off balance but otherwise believe me, you can do it
Perfect time to start a new hobby. Taking your mind off food and start that 1000 piece puzzle that has been laying around. Or go visit that park you’ve been wanting to check out or start your yard project that has been waiting for you.
Avoid the moments in your day that you associate with food. If you usually always have lunch at noon -> go for a walk instead. If you always have a snack when going to the movies, find something else to do
If at any point in time you feel like, no - this isn’t working. You’re unwell. Have headaches (I didn’t have any throughout) then end your fast. Easy as that. You can always retry another time.
Time it right! More on that higher up
If the deep Ketosis is giving you so much energy that you can’t find sleep at night, I highly recommend looking into guided meditation with an app like Insight Timer.
If you’re feeling cold: take a bath, use a heating pad and cozy up. Feeling cold is a natural effect of being in deep Ketosis.
After the fast:
Based on my experience, next time I would have probiotics ready
I believed eggs were a good option to break the fast with. After reading Dr Fungs ‘Complete Guide to Fasting’ I learned that he does not recommend eggs but instead a 1/4 or 1/3 cup of macadamia, almonds, walnut or 1 Tbsp of PB or Almond Butter. A small salad - no dressing. Raw veggies (like the cucumber I had) or a little meat. If you do not eat Keto, some fruit can also be a good option.
Take it suuuuuper slow with eating again after a 100 hour fast. Chew chew chew. Go for easily digestible, non fatty foods. Have probiotics ready
Be prepared for things to taste differently. As you for example stop using sweeteners you might not like foods with a lot of sweetener as you reintroduce them. Listen to your body and if something doesn’t taste good anymore, don’t reintroduce it. Similarly you might suddenly enjoy foods you didn’t before!
Would I do this again? YES! I really loved the experience and next time my goal would be to have a more enjoyable first day off fast. From fat loss, to flat tummy to seeing that we can function great without food and can break these habits of feeling like we have to eat because it is a certain time of day.
This is as much a mental as it is a physical challenge. I know my body even better now which is a huge win.
If you’d like support in trying something like an Extended Fast, check out my Personal Coaching!