Water Fast

(k) #1

I’ve been on keto a few months now. I think I’m fat adapted, can’t be certain as have not used any scientific methods to check meter or sticks.

For the last few weeks I have gone on a water fast to try it. I have done 48 hours and 72 hours. This week am on 72 hours and am thinking of continuing. Are there any benefits in doing so. Apart from calories. I understand there is benefit of autopahagy, how many hours are required, after what mark is the benefit of little gain.

Will doing it for 72 hours or longer guarantee i’m in ketosis.

(Bacon by any other name would taste just as great.) #2

Not eating carbohydrate is what guarantees ketosis. The elevated insulin resulting from eating too much carbohydrate (which is glucose molecules arranged in various ways) is what inhibits ketogenesis in the liver. Low insulin permits it to occur.

Fat adaptation is a different beast. It is the state in which the muscles have healed the mitochondria damaged from too much glucose and reactivated the metabolic pathways that metabolise fatty acids in preference to glucose.

Ketogenesis begins as soon as serum glucose drops low enough to permit serum insulin to drop, as well. Fat adaptation generally takes somewhere around four to six weeks.


You’re in ketosis, that simple. You’ve been eating keto for a few months and did a 72hrs fast. That’s all the science you need. Seems you beat the initial urge most have to be ketosis check happy, but now maybe falling victim to it.

(k) #4

Thank you both for the response.
From what has been posted. My question should have then focused on fat adaption. I understand that I should be in ketosis. Won’t need to do checks.
Trying to figure out if am fat adapted. I have dropped weight, could be a lot of water. I’ll check regularly with measurements.

On fasting, does a prolonged fast have much benefit. Or are 72 hours enough.


Whether or not fasting for 72 hours is worth it might depend on what your goals are for the fast?

(k) #7

My overall goal is weight loss. The fast was to aid that, get fat adapted. I learnt of other benefits such as autopahagy, am interested to learn about the benefits and time it takes for this to occur. Does fasting past a number of days add any benefit. What is the optimum time frame.
I dont want to lose any or too much muscle and here are different points of view on this. Something I need to gain to learn about. As with fasting I will lack my protein macros on those days


How much weight do you wish to lose?

When I first began this WOE in late October - I was very charmed by the idea of fasting. I had just read the “The Obesity Code” and Jason Fung really sells the idea hard.

But if you eat under 20 carbs per day, everyday and don’t snack between meals you will absolutely lose weight without fasting also.

You are the expert on you. Experiment. Try a longer fast if you want, and see what your results are.

With regard to muscle loss, I think that the most important thing is to keep moving.

(k) #9

20 pounds, depends on how it looks. Will know as it comes off.
I have been on 20 carbs a day for some months and have seen a drop in weight. Don’t know how much is water. I am seeing changes in measurements. Must be some fat too.
On the fast i don’t know what is ideal to try, have gone 72 hours. Need to see if a longer time is of benefit. Ass any weight will mostly be water. Am focused on the other benefits too. Will it help with autopahagy. Will it help with any potential loose skin, also need some understanding on what the effects will be on reduced protein.

(Bacon by any other name would taste just as great.) #10

You said you’d been eating a ketogenic diet for a couple of months, so you are most likely fat-adapted. It’s easier for athletes to tell, because they generally notice a decline in their endurance during the adaptation period, and they know that they have adapted when their performance returns to its usual level. If you are feeling energetic, mentally sharper, and well-rested after a night’s sleep, you can consider yourself fat-adapted. Likewise, if you find that you can go hours between meals without hunger and if you find that your hunger is satisfied long before your belly is full to the bursting point.

(k) #11

I’ve read articles on signs of fat adaption as you also mentioned. Working out, my reps are getting harder to do. I am a little slower on some of my runs. In terms of distance I can still go for longer times. I can go without meals, have been water fasting. Was doing IF before keto, so was use to it. Sleep is normal, on the water fast I seem to sleep less hours. I’m meeting some of the signs not others. I guess will know after some months as I measure myself.
Am trying to see if it is worth doing the water fast. Or am I better off doing it every few weeks for a few days and sticking to low carbs.

(Bacon by any other name would taste just as great.) #12

Bear in mind that while endurance returns fairly quickly (within six to eight weeks for most people, but there are always outliers), explosive power takes longer to return (more like six months, from what I’ve been reading). By two years of a ketogenic diet, however, fat-adapted athletes are indistinguishable from carb-adapted athletes, in terms of glycogen levels, etc., the main difference being in their respiratory ratio and in how much longer they can perform on fatty acids without needing glucose.


I don’t know if I am a fat-adapted or not :woman_shrugging: but I do know that the thought of sugar doesn’t make me hungry, while the thought of beef fat does. I bet that is some kind of litmus as well. Bet if you are not interested in sugar, you are not fueled by it.

(Bob M) #14

I’ve done many 4.5-5.5 day fasts. Are they better than 72 hour fasts? It depends on who you ask. Dr. Phinney thinks 4.5 days is too much, while I’m sure Dr. Fung thinks they are OK.

I personally think that as long as you don’t overdo fasting (you can fast too much – if you start getting cold all the time, that’s probably not good), any amount of time is good.

(k) #15

I done it to see if meets my goals, then discovered other potential benefits. I’ll have to look into it before extending for further days. I haven’t been able to find much data on the optimum days for weight loss and autopahagy. When does it start to add little benefit.

(Bob M) #16

You should give up now looking for that. :wink: Seriously…you won’t find anything. Someone like Dr. Fung might have some good ideas, having treated a lot of people, but no one else would know.

And once you start looking into autophagy, it gets crazy. Some are convinced that if you eat any calories whatsoever (particularly protein), you’re out of autophagy. I don’t think the body is like this: there’s rarely an on/off switch.

I look at it like this: longer fasting probably helps to return your system closer to “normal” faster. It’s just there’s only so many of those (or any fasting) you can do before your body can shutdown. And, it’s fun to eat, too.


Seeing if we are fat adapted isn’t so easy, I guess an active person can tell but we less active ones… The experiences differ. I saw a few ideas here and they usually don’t work for me. My hunger changed but there are many factors and fat adaptation isn’t the most important regarding how long my satiation lasts, it’s mostly about what and how much I eat.

I had two milestones. The first was 7 weeks into keto, my hunger and satiation suddenly changed for the better, no more annoying impatient super strong hunger!
The second happened way, way later (but I went off keto all the time as my previous, not very carby woe felt about the same, just easier. still, changes happened) and I don’t lose and gain water weight since that time (it was always +/-4lbs/2kg when I changed between ketosis and not ketosis before. my weight is surprisingly stable. I think it was half of this for months before becoming zero but I rarely weighed myself in those months and the difference is so small and I am a human with a theoretically changing bodyweight so I am not sure). As I never was particularly active, I didn’t notice anything there. Until the last year but multiple things happened at once, maybe it’s all due to my carnivore trials and not stopping my cycling for months in winter… I got significantly better, no doubt. I stopped weightlifting for years (and I still was so weak when stopped) and now I am worse than before my break and improvement is slow, I don’t see a positive effect there yet.
My energy level always were lowish, only my carnivore times could change that (not right away. it gave me zillion instant benefits, this serious one took time, not surprisingly), this change was definitely long after I lost my water weight changes so I am sure extreme low-carb was the key.
I think my hunger changed around the second milestone too but it was more gradual. The first change was very sudden.

I am not sure it helped any but here, my experiences, they may be interesting for someone. I always like to read how individual we are.

I personally don’t want to go over 72 hours but I feel the need to eat very very nearly every day, often multiple times so it doesn’t matter (I had only one longer fast in my life, in my high-carb times. it was easy due to pure determination and curiosity. I couldn’t do that now. I didn’t notice fat adaptation or ketosis helped much with fasting though my average eating window did diminish at some point). If you have enough fat reserves and feel good, a longer fast may be fine but I am not knowledgeable about it (I theoretically don’t even have enough extra fat for such a long fast without problems. but in practice, I can’t tell without seriously trying and maybe not even so). 72 hour fasts now and then should help enough with fat-loss and autophagy alike and they seem safer to me than longer ones. Some people tend to overdo fasts too.

(k) #18

I agree, theres a lot of opinions, don’t think will find any hard evidence. I guess it’s seeing what works for me. Unless i find a reason to do so. Maybe long fasts are not ideal. if I think it helps with extra weight loss can try it for longer. Otherwise might stick to trying it every other week.

(k) #19

I’m quite new to it. Will try different things and see what sticks. I would like to see how quickly i can come in and out of fat adaption by testing my carb edge. Might have to try that when I can regularly take readings. Haven’t done that up to now. Have stuck with 20g, maybe go to 30g and see if I keep dropping weight. You don’t always see the scale shift in a week, don’t want to break the cycle for too long


As far as I know, my fat adaptation (almost?) never went away, not even when I ate much more carbs for months. At least I didn’t get back my old hunger that suddenly disappeared after 7 weeks on keto. I still did low-carb most of the time, it matters. When I was at my worst , I started to feel my hunger starting to change at some point, I run back to keto then and it changed back right away.
I can’t possibly know what happens inside but it seems there is a very close connection between my hunger and some basic level of fat adaptation…

I heard similar things about others: fat adaptation doesn’t leave us right away just because we eat more carbs for a while.

We come out of ketosis quickly, not fat adaptation.

Weight loss is weight loss (and I mean fat here), it doesn’t necessarily say anything about ketosis, one can happen without the other just fine. maybe it does in your case, who knows. But hunger and satiation changes may stay with us after keto for a while (or longer if they are part of our fat adaptation and we keep that), maybe we change habits and those help… So keeping losing fat doesn’t necessarily mean we are still in ketosis.


Correct, you should forever change the term “weight loss” to FAT loss in your head. That’ll keep your mindset right. Use the scale to see trends in progress, but take measurements at least every 2 weeks. Body recomposition is slower but ultimately what you want.

I lost a lot of muscle when I was loosing “weight” and it sucked! Don’t do that.