ex_fast: 5 day water fast, down 2lbs. Repeat.

Fasting after 2 years of PUFA-avoidance.

I recently did a 5-day water fast, then a “refeed” on ex115 for 7 days. Then I did it again.

My History with Fasting

As detailed in 19 Fat Loss Experiments I’ve Tried at & Failed, I have quite a history with extended water fasting. I didn’t start tracking my weight permanently until late 2017, but I did a bunch of water and low-caloric fat fasting (not ad-lib like I have recently) just before that, when I was down to around 200lbs.

You can see the very distinct fasting pattern many times in my weight chart

When I moved back to the U.S. in late 2016, 100lbs lighter than I had left, I began rapidly regaining weight, despite still doing strict keto and cooking most of my meals at home. I tried to utilize fasting to slow or reverse this rapid fat gain, but it didn’t work very well, as you can see in the graph.

I mostly gave up on it, because it just didn’t work. I’d regain any weight I’d lost immediately upon refeeding, and I felt miserable the whole time. One time I got sick during a fast and had to take 2 weeks off work. Good times.

At one time I tried fasting near my all-time high of 300lbs, when I was in the morbidly obese category. Confusingly, I could barely fast for 3 days before incurring starvation-like symptoms: hunger pangs, constant thought of food (mostly steak), inability to sleep or concentrate.

When I was at 200lbs in 2017, 3 days was no issue at all. I did several 5-day water fasts back then that went pretty smoothly, and my longest water fast was 7 days. That one included a bunch of white-knuckling at the end, barely sleeping for 2-3 nights in a row.

My record on a “coffee w/ cream fast” was 10 days back then, involving maybe 500kcal/day from the cream.

Somehow, fasting was SIGNIFICANTLY easier at 200lbs than at 300lbs, despite carrying around a literal 100lbs of extra fat. How could this be possible? Mainstream theory would predict exactly the opposite, and even when I talk to fasting proponents that follow Jason Fung or similar, they just tend to not believe me.

They’d say that I just need to “make it through” to that magical other side of a fast where it is just easy & trivial and you can go on for 140 days like that Scottish guy Angus. But this was all on heavy keto, I was in “fat burning mode” the entire time even before starting those fasts.

Unfortunately, I think they are wrong about “making it through,” at least I never did.

Does PUFA mess up fasting?

Of course, back then I didn’t know about Modern PUFA Theory (MPT). I had likely lost the 100lbs while living in Asia for 2 years not just because of keto, but also by just living in a society that eats way lower PUFA than America, and way lower protein too. Many Asian street food meals include 100-200g of meat - if you’re lucky. A tiny portion of vegetables for flavor, and the rest is all rice. As a ketoer, I of course didn’t eat the rice. I supplemented heavily with heavy cream from the import store and fancy New Zealand butters.

But presumably, if I lost my original 100lbs while living in Asia due eating relatively low PUFAs, I would’ve been pretty PUFA depleted after that. For one I was just the lowest in total body fat I’d ever been, and also I’d likely depleted very effectively for 2 years in a row.

Since I didn’t eat the rice in these meals, even the cooking oil PUFAs would’ve been relatively low in stir fries. Whatever got stuck to the surface of a small portion of meat and vegetables. My own supplemented cream & butter & so on would’ve been close to zero PUFA.

I had been accidentally avoiding PUFAs, eating low-protein, and attributed all the winning to keto.

Funny how that works.

But after returning to the U.S. and eating a “Standard American Keto” (SAK) diet of ribeyes, half a package of thick-cut bacon, 6 eggs, restaurant salad dressing (when going out occasionally), roast chicken with the skin on (“fat is good!”), and snacking on nuts at the office all day, I would’ve loaded myself up on PUFAs like nobody’s business.

It is actually difficult to imagine a diet higher in PUFA than SAK. Maybe if there was more focus on pork & chicken than beef, but they do celebrate bacon and fatty chicken with the skin on, and nuts.

If it is indeed true that linoleic acid, the omega-6 PUFA, wreaks havoc in your system, then having stored the better part of 100lbs of it would… well, wreak continuous havoc on your system just from adipose flux.

I never took an OmegaQuant then, but it must’ve been very bad. Let’s assume I had 25% linoleic acid in my adipose tissue after eating SAK from 2017 to 2022, when I hit 300lbs. 5 years of PUFA maxxing!

If all of this is accurate, then it’s completely understandable that I could easily fast for 5 days with few issues when I was 200lbs and PUFA depleted, and that I could barely do 3 days at 300lbs with maybe 25% LA in my system.

In fact, the extra fat would be bad, because I would be getting a higher total amount of LA into my system every day.

If we ask the Linoleic Adipose Flux calculator, at 150lbs of fat mass and 25% LA, I would’ve gotten 133g/day (!), or 1,200kcal/day (!!), or 17tbsp of soybean oil (!!!) per day BEFORE EATING any seed oils.

And, of course I was eating seed oils. I was refeeding on eggs & bacon and In’n’out low-carb burgers w/ soybean oil spread. 1 double-double has about 14g worth of soybean oil unless you ask them to hold the spread, 2 of those was my standard order. I was eating whole roast chicken from Costco. If I went out to a restaurant, I’d get the salad w/ the “ranch” (=soybean oil) dressing.

So is it a miracle that I couldn’t fast at 300lbs?

Why water fast now?

Now that I’ve been aware of the whole linoleic acid issue and am down over 75lbs again, with some pretty extreme & strict PUFA avoidance for over 1.5 years under my belt, I thought it might be an interesting test.

If PUFA theory is correct, I should have a much easier time fasting now than at 300lbs. Since, back at 200lbs, I wasn’t consciously avoiding PUFAs and still eating out at restaurants and so on, maybe I should be even better at water fasting than then?

In addition, people had been bothering me with “Have you tried fasting?” and I’d always said “Yes, but..” and the “but” part had just pretty significantly changed since I first started giving that answer.

It would also be a fun thing to just test out this hypothesis. If, at 220lbs or so, I’d be unable to fast comfortably for more than 3 days in a row, that wouldn’t bode well for MPT. Nearly 2 years of strict PUFA avoidance should’ve roughly cut my adipose LA % in half.

Of course it wouldn’t be enough to drive it to ancestral levels of 2-3%, but neither would’ve been 2 years of accidental PUFA avoidance in Asia back then.

In short: my ability to water fast should be an indicator or “symptom” of how well my metabolism was functioning. I would not white-knuckle it or use ANY willpower. The second I got any symptoms like feeling excessively cold, inability to concentrate or sleep, or obsessive food thought, I would quit the fast.

To paraphrase my friend John from The Heart Attack Diet:

I resist willpower at all cost.

Why not dry fasting?

Back when I did fasting in 2016/2017, dry fasting was pretty much unheard of, from what I remember. Some crazy people knew of a guy who lived on a mountain and did it once.

These days whenever I say “water fast” there will be at least 1 person questioning why I didn’t do a dry fast. To be honest, I’m curious about dry fasting, but I haven’t dared do it. People say there are significant dehydration risks, and to be careful. And it’s the summer right now.

But I’ll probably try some dry fasting in the fall or winter time.

The Refeeds

Another big difference this time would be my controlled refeeds. In the past, almost all my extended fasts had ended in white-knuckling it, using as much willpower as possible in the hope of “breaking through” and “making it” and thus several days of obsessive food thought, doomscrolling through pictures of steak, and watching hours of YouTube videos of people cooking.

Then, I’d go to the store, buy everything (keto) under the sun, and refeed on half a package of bacon, half a carton of eggs, a t-bone steak, an avocado, a bag of mixed nuts w/ full-fat yogurt & dark chocolate pieces broken into it..

And by the time my first meal was over, I’d regained all the weight.

This time, I would refeed by going back to the diet I was doing beforehand, ex115. It wouldn’t be high in PUFA, it wouldn’t be high in protein. It would keep insulin very low, hopefully preventing too much fat-regain.

Of course I still expected some or much of the weight lost during a water fast to come back. Most of it is, after all… water.

Tale of the Tape

The short version is that, both times, I felt absolutely nothing until late day 5, and then I couldn’t fall asleep and quit the fast the next morning.

It was pretty wild, actually. I’d say both of these 5 day fasts were significantly easier than my previous 5 day ones, where the last 2 days had already involved some willpower, struggle, and sleep issues that I’d just fought through, hoping to “make it to the other side.”

I felt so great in the evening of day 5, both times, that I thought things like “Wow, I’ll fast for 30 days straight” just hours before doing to bed, only to find out I couldn’t fall asleep at all, tossing and turning for 6h before finally giving up.

Maybe the only other downside besides the sudden “sleep wall” on night 5 was the psychological (?) factor. Just not experiencing any flavors or stimulation was … weird. I really, really like the taste of coffee with cream, and beef, and tomato sauce.

Unfortunately, I hate black coffee. I can kinda stomach espressos, but mostly because they’re so tiny, which defeats the purpose.

I ended up making up for it with energy drinks, drinking mostly Jocko Go (monk fruit sweetened) drinks and Monster Zero (the white ones), which contain sucralose & erythritol. The Monsters gave me the burps, probably from the erythritol. But at least I had some routine, some flavors, something to enjoy.

I don’t know if I should call this psychological, or hedonic, but it is a factor.

My workout performance in many exercises went absolutely into the shitter. Most exercises I could only do 1/3 the reps I could previously do on ex115, although I actually broke PRs in some too. So despite ex115/ex150 already being pretty glycogen depleting, the water fast was dramatically more so.

Net Loss

Now let’s see how I did weight-wise.

Like we’d expect from a water fast, my weight dropped dramatically. “Number Go Down!” is a fun game to play on a water fast, since I tend to lose about a pound daily, very reliably. It’s not uncommon to step on the scale in the afternoon and see a lower number than I did that same morning.

At the very end of the 2nd fast, I saw “210” on the scale. A surreal feeling, as I haven’t seen that number since 2017.

But the big question, did I end up losing weight long term, or was this just temporary fluctuation again? Did I regain it all on the refeeds?

I’ve drawn helpful yellow horizontal lines onto the chart. You can see the following:

1. I was roughly averaging 221lbs toward the end of ex115, before the fasts

2. After dipping to 214.5lbs during the first fast, I regained back up to around 218lbs on average.

3. The second fast dropped me to 210.8lbs, and I regained to about 215.5lbs so far after 9 days.

Interestingly, there is a slight “over correction” both times where my weight goes up and then comes down again, and I’m actually lower day 7 than I was day 5-6. That’s why I didn’t chose the very peak but 1-2 after for the yellow lines.

I don’t know if this is just random noise, or an actual refeed phenomenon, or what.

2-3lbs net loss each fast?

Overall, that’s not half bad. Of course, the majority of the weight lost during the water fasts was water/glycogen. But I seemed to stabilize around 3lbs lower after the first fast, and about 2.5lbs lower after the second.

If that holds true, and we calculate the entire time, that means about 2-3lbs lost during 5 (fast) + 7 (refeed) days. If we were to extrapolate that to a month, we could do 2.5 of these fast/refeed cycles, and potentially lose 6lbs.

Of course, naive extrapolation is the devil’s workshop, as they say. They do say that, don’t they? Let’s not blindly extrapolate and declare victory prematurely.

In order to see if I’m now permanently at 215lbs, I’m not just doing another 5 day fast and so on. Instead, I’m doing a regular old run of ex115 for 30 days.

If eating my normal diet ad-lib for 30 days doesn’t make me regain significant weight over the post-fast settling point, I would judge this a pretty good strategy.

If it does, however, and I end up back at 221lbs, then it’s not a good strategy. After all, it’s not useful to temporarily starve yourself down to a weight and then, upon eating normally, regaining all of it. That maybe makes sense if you want to fit into a specific dress size for a wedding, but not in the context of long-term health. Suffice it to say I am not looking to fit into a dress any time soon.

The only “gainz” (or losses) I care about are lasting, and without incurring metabolic damage. I’ve played the “Number Go Down. Oh nooo, rebound!” fasting game enough in my life to not be interested in it.

I’ll know more in another 3 weeks.

Buffers: explaining the water weight loss/gain

Both times, I lost about 7lbs in 5 days, but only 2-3lbs “stuck” and were therefore probably fat losses instead of temporary glycogen/water weight.

I think this could probably be explained by certain energy buffers we have in the body:

1. Muscles (and other cells) contain a certain level of ATP, ready to use.

2. Muscles & liver contain a certain level of glycogen to back-fill the ATP lost.

An adult human can store about 500-650g of glycogen in skeletal muscle & liver. I’m a slightly above average size adult male human, so let’s just go with the 650g. If each gram of glycogen contains 4kcal like a gram of crabs (I couldn’t actually find any data on this), that’s about 2,600kcal total.

Of course your glycogen might not be at 100% unless you just got done carb-loading for a marathon, and it probably doesn’t go all the way to 0% unless you die during the fast. But let’s just take that as a back of the envelope number.

I don’t know how many carolies would be in the ATP buffer currently in our muscles/cells.

If we do more back of the envelope heat energy math, we could come up with the following:

Total loss in 5 days:        7 lbs
Fat lost:                    2.5 lbs
Bounced back (buffers):      4.5 lbs
Water bound by 1g glycogen:  3-4 g (not sure)
Total glycogen buffer:       500-650 g
Total glycogen weight swing: 2,000-3,250 g (4.4-7 lbs) 

This actually makes total sense. I likely have higher than average glycogen stores, but I didn’t deplete them fully. And they probably weren’t loaded fully to begin with on my very-low-carb, very-low-protein diet.

The 4.5lbs of “buffer swing” is easily explained just by the glycogen and associated bound water.

I think this also partly explains why caloric restriction is so ineffective. There is a ton of energy buffered in your system that the body can simply draw down before any fat loss begins. If I had run a moderate caloric deficit of say 250kcal/day, how many days until I would’ve even burned through the glycogen? Easily 10 days.

You simply can’t ignore all these mechanisms and just go “CICO so there you have it it’s THE LAW” and expect that to actually work. You’ll probably just bounce in and out of your glycogen buffer for your entire weight loss career, never losing much fat if any.

RMR on day 4 of a fast: 2,220kcal/day

Oh yea, I almost forgot to mention this: I did a Resting Metabolic Rate test via indirect CO2 calorimetry on day 4 of the first fast, and it came back as 2,220kcal/day. That’s only 60kcal lower than the last one, which I did fully fed.

That was kind of crazy to me. After 4 days of consuming no carolies at all, my RMR basically hadn’t dipped at all?! That would mean my body was still firing on all cylinders, happily living off adipose flux.

No metabolic down-regulation, no systems offline or in degraded performance mode. That would explain why I’d felt so great, had zero appetite, cravings, or any other metabolic side effects.

Speculation: Why no fasting issues, then the sleep brick wall night 5?

So how come I hit that brick wall with sleep on night 5 both times? If there were absolutely no other starvation symptoms?

One theory that makes sense, which my friend Mike from ‘stralia proposed: after sufficient fasting (a few days), the body becomes hyper sensitive to stimulants like caffeine.

I had opted to replace my coffee/cream intake with sugar-free energy drinks, both so that I’d have some flavors, some routine to look forward to, but also to not do caffeine withdrawal at the same time as the fast.

A Jocko Go drink has about 95mg of caffeine per can, Monster Zero Ultra apparently around 140-150mg. At a rate of maybe 6 a day, that gets me to a similar amount as my regular (very high) coffee consumption.

I wasn’t consuming more caffeine than normally, maybe even a little less on average. But if my caffeine sensitivity somehow went way up (or, rather, back to a normal person’s) after 4-5 days on the fast, that could explain the weird discrepancy - feeling totally normal & no real measurable RMR drop, yet going from sleeping totally fine night 3 & 4 to total inability to sleep night 5.

I suppose, for science, I should give up caffeine for the next water fast and see if anything changes. Ugh! I can’t think of anything worse than giving up caffeine. Then again, I suppose I wouldn’t be able to drink coffee or energy drinks on a dry fast, so eventually I’ll have to do it at least once.

You people don’t understand how much I like coffee w/ cream.

Choice Notes

This thing is long enough already, and many of my notes aren’t all that interesting, but here are a few to give you an impression of what it was like:

First fast

Day 1:

Almost accidentally bought a latte lol, gotta think about this
2 zero-sugar energy drinks to make up for the sudden lack of caffeine
Very mild headache on and off in the afternoon, gone by evening (caffeine withdrawal?)

Day 2:

Mild headache in the morning, went away after energy drink
Definitely caffeine lol
Had espresso cause no milk/cream in it
Mouth kinda mealy no matter if I brush
Ketones only 3.0mmol/l - sad! That's worse than I usually have lol
2h later, 4.8mmol/l - yay!
3pm: 4.5mmol/l
CGM tending toward <70mg/dL (hypoglycemia) all day unless I'm actively walking around
6pm: 5.3mmol/l

Day 3:

Mouth super sticky/mealy no matter how much I brush my teeth

Day 4:

Still 2,200kcal in the RMR!
Drank 6 energy drinks lol
For the record, temps still mid 98°F most of the time
New deadlift PR, and by quite a bit! Surprised.

Day 5:

Still nothing in terms of hunger
Very slight stomach feeling around lunchtime, not even a rumble (happened to be in a food court at the time)
Had 6 energy drinks & 1 espresso
Had bowel movement today (still on day 5!)
Chest press PR
Evening:
Getting lightheaded when standing up rapidly
BHB 6.7mmol/l, new record
Night:
Tested “HI” on the keto meter! (>=8mmol/L)
Feeling kind of wired/amped up when trying to fall asleep, stress setting in?
5am:
Woke up pretty wired, can't fall back asleep
Decided to abort fast
Haha, how fast it can go from “fine” to “fucked”

As you see in the notes, I did actually set new PRs for some exercise, but totally crapped out in others. I noticed this years ago when fasting, around 2016/2017. I think the adrenaline from the fast lets you “go harder” in some ways, but since you have way less muscle glycogen, that’s not enough in others. Deadlifts especially seem very “how hard can you go” for me, whereas e.g. squats or overhead press seem much more like a “resource limited” exercise, where I’m just watching myself burn the fuel until it’s all gone.

And I can now say that I’ve maxed out the keto meter at 8mmol/L, a point of keto pride :) If anything, the fast was worth it just for that, lol.

Here’s a screenshot of what my CGM looked like for the latter half of the fasts. Of course the ketard in me wears constant hypoglycemia with pride.

The second fast had significantly fewer notes, it just wasn’t as exciting, just more of the same.

Second Fast

Day 5, evening:

Still haven't noticed anything .. will I hit the wall tonight?
Last few days constant desire to brush teeth, think this is what some people get when first getting into ketosis?
3am: still haven't fallen asleep lol, same thing again
5:30am: Still awake, worse than last time
6am: well it's technically day 6 and the fast is over. Drank 2 cups of cream, hoping it'll help me get some sleep
Weird: still haven't been hungry a single time since beginning of fast
Lowest weight I saw was 210.85lbs, bizarre to see 210 on the scale
Fell asleep about 30 minutes after drinking the cream
Woke up around 9:30am, so only 3h of sleep. But my circadian rhythm seems unchanged (that's my normal wake up time w/o an alarm) it was just being unable to fall asleep. Adrenaline?

The little spike on this CGM screenshot are the 2 cups of cream I had at 6am to end my fast. I fell asleep quickly after that, slept for about 3.5h (about 2 ultradian cycles), and then woke up as normal, and my glucose was normal after that.

Conclusion: I can fast pretty good, yay!

If we just view this through “ability to fast is a symptom of metabolic function” then this was a huge success. Practically no symptoms, RMR unchanged after 4 days of fasting. Besides the (pretty intense) sleep issue, it was perfect. By far better than when I fasted regularly in 2016-2017.

And even with the glycogen rebound, 2.5lbs of fat loss for 12 days’ effort is pretty great! Especially for where I’m at now, where I don’t lose 10-20lbs a month any more like I did at 290lbs.

We’ll have to see if this is a viable long-term strategy, and that’s why I’m still doing ex115 right now. If I don’t regain significant portions of the weight lost during the fasts, I might just try doing this again, and maybe force myself to quit caffeine for the duration (UGHHHHHH!). See if the sleep issue still occurs.

But even if 5 days is somehow the limit even without caffeine, a 5+7 until it stops working strategy might be in order.

We’ll see.