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First Multi-Day Fast

If you just want to watch a recap of my fast, skip ahead to the post-fast video.


Starting now you can’t eat for three days. How do you feel?

  • cranky
  • ballistic
  • ehh…
flying man showing teeth and spear
Is this what you look like after a few hours without food?

When I mention a three-day fast to anyone, I hear “cranky” or “ballistic” often and “ehh…no big deal” never. I hear about intermittent fasting all-the-time but haven’t met anyone doing a multi-day fast. It feels scary. It was for me too. Prior to 2018, I felt like I had to eat every three hours. My old executive once said to me, “Are you ever not eating?” I lived by six meals a day for strength, bodybuilding, metabolism. Not that my metabolism needs help. I’ve always been skinny, just with a bit more muscle since college.

Since I healed my gut issues in 2018, I’ve frequently restricted my eating window to four to eight hours per day. This intermittent fasting/time-restricted feeding isn’t a weight-loss strategy for me. It reduces my blood glucose variability and it helps me digest food predictably which is critical for a Type 1 diabetic giving insulin with peak effect over a four-hour time period. If the meal digestion is delayed by two hours, my blood sugar goes low then high later.

If your answer above is “cranky” or “ballistic”, I understand. In 2017 fasting for three days would be my own personal horror movie. After healing my gut and completing fasts easily, I wonder about gut health and the impact on eating habits. I wonder about how many carbs people eat and how well they metabolize them. I wonder if they’re on a path towards pre-diabetes. I wonder.

I’m not the expert and I’m the worst at metabolizing carbs. I’m a diabetic. Unlike many diabetics, I have low body fat and a good amount of muscle which helps with insulin sensitivity. But still, if I eat thirty grams of carbs (a banana) I will be cranky two to three hours later when my blood sugar drops. I will want to eat again because I will feel cranky. Eat a hundred grams of carbs (~4 slices of pizza) and I will go ballistic two hours later with that blood sugar drop. That doesn’t mean carbs are bad. I’m not good at metabolizing them. If you get cranky from moderate amounts of carbs or ballistic from larger amounts, you might not be the best at handling carbs either. Maybe your pancreas needs a break. Maybe. Just my opinion from reading and listening to smarter people than me with medical degrees.

Another major factor in why I ate so often was the high-level of candida (yeast) in my gut. In the 2010s I was so hungry so often, I feel like the yeast was running the show “Eat Matt, eat. You know you want to.” Treatment in 2018 reduced my candida level. Finally, I could skip meals without feeling like I was dying. And I did.

This multi-day fast is my attempt to take fasting up a notch. Why? Maybe only to answer “Ehh, sure” if anyone ever asks me to do something that requires skipping food for a few days. It feels good to have that power. Maybe to trigger some autophagy but that might take a longer fast. Baby steps. Maybe like a man running a once-in-a-lifetime marathon, just to say I did it.


Over the last couple of years, I hoped to try a longer fast. But first I had to master shorter fasts from twelve to twenty-four hours, gradually ramping up from twelve over time. Recently, I completed several twenty-four-hour fasts. It was no big deal. I heard burning ketones helps with fasting, so I targeted waking up between .5-1.0 mM BHB. Throughout the day my BHB ranges from .5-2.0 mM typically. Burning more ketones provides an alternative fuel source for your body and brain. I’m extra-productive when I skip breakfast and lunch. Sometimes, I get hungry mid-afternoon and eat a salad with tuna or some macadamia nuts. I’m not a zealot when I fast. If my body is yelling for food, I eat.

When I don’t eat for a day, I’m most hungry between 3-7 pm. For a multi-day fast, I planned fun (or at least mentally engaging) activities during those timeframes. Being bored or stressed makes fasting harder. After the preparation above, however, I’m not as easily swayed by these impulses to break down and eat. I find something productive to do or relax and remind myself that I’m not hungry. Eventually, the hunger passes. That’s the control I want.



  • Drink water-only except for coffee, tea, mineral water and lemon.
  • If I need to break early, try macadamia nuts rather than a complete meal to continue.
  • Use single glucose tablets if needed for blood sugar <60 mg/dL.


  • salt tabs
    • wake-up – 2g
    • afternoon – 2g
    • as needed – 1g
  • magnesium
    • wake-up – 2 Slow Mag (150mg) + 2 citrate/malate (250mg)
    • afternoon – 2 Slow Mag (150mg) + 2 citrate/malate (250mg)
  • skip everything else


  • If I can’t sleep, use melatonin, magnesium, phosphatidylserine, gaba combo
  • No tryptophan, glycine, amino acids


  • General – lift heavy to mitigate muscle loss, take longer rest
  • Hip Hinge – deadlifts, hang power cleans, kettlebell swings
  • Pull – pull-ups, inverted rows, machine rows
  • Push – bench press, military press, push-ups
  • Core – crunches, obliques, planks
  • Schedule
    • Thursday – hip hinge, pull, push, core
    • Friday – hip hinge, pull, push, core
    • Saturday – long CrossFit WOD mid-morning

Break fast

  • This is literally “break fast” not breakfast (i.e. my first meal after fasting)
  • I don’t want this to be too large or heavy because I haven’t digested anything in a few days and the stomach contracts, although maybe not much in only three days.
  • 2-3 scrambled eggs + greens or veg

Pre-Fast Day 0

Wednesday 12/18

  • Last meal finished by 9 pm
  • Ate a big ribeye steak with butter, mushrooms, onions, garlic, sage with olive oil, heavy salt, pepper
 Day 0Day 1Day 2Day 3Day 4
Weight (lbs)189    
Body fat %10.4    
Blood sugar @8 am (mg/dL)109    
Ketones @8 am (BHB mM).6    
Ketones @12 pm (BHB mM).3    
Ketones @6 pm (BHB mM).6    
Insulin 24-Hr Total (units)33    
Peak Hunger (1-10)3    
Deep sleep (min)37    
Sleep HRV (ms)35    
Resting HR low (bpm)51    

Fast Day 1

Thursday 12/19

  • Morning
    • Work
  • Afternoon
    • Exercise – 5 sets x 5 reps
      • Heavy Deadlifts
      • Bench Press
      • Upper Back Machine Rows (5×10)
      • Weighted Exercise Ball Crunch (30 reps)
    • Work late
  • Night
    • Watchmen, West Wing
 Day 0Day 1Day 2Day 3Day 4
Weight (lbs)189190   
Body fat %10.410.8   
Blood sugar @8 am (mg/dL)109112   
Ketones @8 am (BHB mM).6.9   
Ketones @12 pm (BHB mM).3.5   
Ketones @6 pm (BHB mM).61.1   
Insulin 24-Hr Total (units)3316   
Peak Hunger (1-10)36   
Deep sleep (min)3753   
Sleep HRV (ms)3538   
Resting HR low (bpm)5148   

Remember when reading the stats above that my morning glucose level isn’t indicative of a normal person fasting. Non-diabetics should drop in the 60s-80s when fasting. My glucose is regulated by an open-source automated insulin pump. I have it set up to be uber-conservative during the fast since only .2u of insulin could drop me to 50 mg/dL when normally my blood sugar would barely budge.

My hunger peaked around 6 pm after walking fast for a little while. I wouldn’t walk at a fast pace for a long time on my first fast. It makes me extra hungry. Hunger was much less than I expected.

I’m excreting a lot of fluid. I’m drinking plenty of extra water too. This was expected but this is the most inconvenient part of the fast. Expect to wake up several times overnight to go to the bathroom.

Senses seem to be heightened a bit. Clearer vision. Shaper hearing. But my senses go up and down so I can’t tell if this is due to the fast. I’m much sharper mentally though.

Fast Day 2

Friday 12/20

  • Morning
    • Work
    • Exercise – 5 sets by 5 reps
      • Hang Power Clean
      • Overhead press
      • Pull-ups (3×11)
      • Oblique Crunch (30 reps)
  • Afternoon
    • Work
    • Physical therapy/ART for head, neck, back
  • Night
    • Baby
    • Pack for beach
 Day 0Day 1Day 2Day 3Day 4
Weight (lbs)189190185  
Body fat %10.410.810.4  
Blood sugar @8 am (mg/dL)10911296  
Ketones @8 am (BHB mM).6.92.2  
Ketones @12 pm (BHB mM).3.51.8  
Ketones @6 pm (BHB mM).61.12.1  
Insulin 2-Hr Total (units)331615  
Peak Hunger (1-10)365  
Deep sleep (min)375355  
Sleep HRV (ms)353857  
Resting HR low (bpm)514846  

Both the 56ms heart rate variability (HRV) and the 46bpm resting heart rate (HR) above are personal records by a lot. Normally my HRV is 30-35ms and resting HR is 49-51bpm. Those numbers don’t improve that much at random. The only other change I’ve made that improved them that significantly is dropping my HbA1c (3-month average blood sugar indicator) from 6.0% to 5.5%. I also noticed my heart rate is generally lower throughout the day.

oura graph showing 46 bpm heart rate and 57 ms heart rate variability
This shows my heart rate stats from Thursday night to Friday morning. You can see how the numbers trended better during the fast.

Hunger is even less today, still peaking around 3-6 pm. I’m looking forward to breaking the fast tomorrow, but not obsessed. I’m contemplating going another half-day until Sunday morning.

This is also my best blood sugar day of the fast (graph below), mostly because I had a long cardio workout Saturday and I accidentally turned off a pump setting that delivered my normal amount of insulin which sent my blood sugar WAY down, requiring me to eat one glucose tablet. That insulin sensitivity is a great thing, just not automatic for a diabetic. Fasting is more complicated for diabetics due to the vastly different insulin and medication needs. Be careful. Talk to your doctor.

stable blood sugar graph from Day 2 of the fast
I’d expect my blood sugar would be in the 60s-80s most of the fast if I wasn’t a diabetic. The spikes are from the limitations of my automated insulin pump system. Automated is not as good as a normal person’s automatic blood sugar regulation.

Fast Day 3

Saturday 12/21

  • Morning
    • CrossFit EWOD
  • Afternoon
    • Baby
    • Finish packing for beach
    • Haircut
    • Drive to beach
  • Night
    • Birthday party
    • Break fast at 9 pm
 Day 0Day 1Day 2Day 3Day 4
Weight (lbs)189190185184 
Body fat %10.410.810.49.9 
Blood sugar @8 am (mg/dL)1091129694 
Ketones @8 am (BHB mM). 
Ketones @12 pm (BHB mM). 
Ketones @6 pm (BHB mM). 
Insulin 24-Hr Total (units)33161514 
Peak Hunger (1-10)3653 
Deep sleep (min)37535554 
Sleep HRV (ms)35385742 
Resting HR low (bpm)51484647 

I could have kept going until Sunday morning or longer. I wasn’t that hungry. The only thing bothering me was the amount of liquid coming in and out of me. Plus, my lips were a bit dry, maybe mildly dehydrated at different points during the day. Mineral water helps a ton. The main reason I broke the fast is many family holiday events over the next few days. I don’t know how digestion will ramp back up and I don’t want to be sidelined for a few hours. It was nice to get this alert from the Zero app.

zero fasting alert showing I completed a feast of 72 hours, 30 minutes

Workouts throughout this were easy. It helped to take longer breaks on the heavy lifts but I could have pushed the pace more. I went slower on a long cardio workout than normal but still averaged 140 bpm heart rate for thirty minutes.

Ketones peaked at 4.8 mM. I’ve been this high before when I was strict ketogenic for a few months, but numbers this high are rare and perfectly safe. Ketones this high also make the fast easier because my body and brain have plenty of fuel just switched from primarily glucose to primarily ketones.

Ketones showing 4.8 mM and blood sugar showing 94 mg/dL.
4.8 mM is my BHB ketone level. 94 mg/dL is my blood sugar. That graph is my blood sugar over the prior hour. Stable. Fasting = stable glucose.

I broke the fast with three eggs sunny side up in butter, mushrooms, tomatoes, and sage in olive oil and lots of salt. I planned not to eat too much and ate maybe a little more than planned but not a heavy meal at all. Tons of salt. The best eggs of my life :)

a plate of eggs, mushrooms, tomatoes
Eggs, glorious eggs.
Salty, salt, salt.

Digestion is fine. No issues.

Post Fast Day 4

Sunday 12/22

 Day 0Day 1Day 2Day 3Day 4
Weight (lbs)189190185184 
Body fat %10.410.810.49.99.4
Blood sugar @8 am (mg/dL)1091129694 
Ketones @8 am (BHB mM). 
Ketones @12 pm (BHB mM).
Ketones @6 pm (BHB mM). 
Insulin 24-Hr Total (units)33161514 
Peak Hunger (1-10)3653 
Deep sleep (min)37535554 
Sleep HRV (ms)35385742 
Resting HR low (bpm)51484647 

I didn’t take all the measurements on the morning after I broke the fast, just those I was most interested in.

My final body fast was ~1% less than what I started at (10.4%-9.4%). That means I dropped ~2 lbs of body fat (1% x 185 lbs). That makes sense because I burn ~3500 kcal per day, ate nothing except you could count the ~1500 kcal steak dinner Wednesday night for fueling me into Thursday morning. Two pounds of fat is enough energy for about two days. Glycogen stores ~800 kcal of energy and were likely significantly depleted. That adds up to almost the ~10,500 kcal I’d need over three days. The math adds up.

Post-Fast Video Recap

If you want to know if I survived not eating for three days or just want a recap, watch this.

Post-Fast Thoughts

I will do another fast, maybe three days, maybe five, maybe eventually seven days. Fasting multiple days was much easier than expected. I felt great mentally and fine physically, although I didn’t push it. The only thing I didn’t like was the constant water in and out. But for my blood sugar control, mental clarity, digestive rest, simplicity of life, and maybe a little autophagy, I’ll do it again. It helps to be well-prepared. Reach out if you have questions. Use a doctor if you have medical issues. Be careful.

If you ever want to join me on a feast, let me know.

Happy fasting.

Happier feeding.