Water only fasting and ketogenesis

I have spent over 30 years as a physician who specializes in the supervision of patients who use water-only fasting to deal with chronic disease issues. With water-only fasting, your body uses stored glycogen for fuel for about a day. If still no food is available, then protein is used for fuel for about another day. After that, with still no food available, the body wisely shifts to burning fats for fuel - ketogenesis. Ketogenesis begins after about 48 hours of fasting and continues for the duration of the fast. Metabolic ketogenesis is the body's natural adaptive response to a lack of available food.

The fundamental reason fasting is so supremely helpful for the vast majority of diseases is this: When food is not available, and is not likely to be available for some time, the body must do everything it can to survive. Once ketosis has kicked in, the body is on autopilot regarding its fuel source. Fats will be consumed as long as they are available, which is about 5-6 weeks for the average person. Ideally speaking, in order to survive for as long as possible, all systems, organs, tissues and cells should be in optimal condition. The body must quickly minimize or eliminate any weak links. That way everything can work together, optimally, to give the best chance of long-term survival to get through the current famine. So, the body gets to work, and gets to work intensely, repairing damage, removing obstructions and optimizing functions throughout the body. I have witnessed amazing and miraculous healing occurring right before my eyes on countless occasions. Our bodies are truly fearfully and wonderfully made.

My point with all of this is to demonstrate that the condition of ketosis is indeed proper and laudatory when fasting. It is a most excellent survival strategy built into all mammals. As a side effect fasting greatly helps your body heal itself form all kinds of maladies.

However, artificially creating and maintaining the condition of ketosis through a strict and measured diet for long periods of time is difficult. There are numerous aspects of the ketogenic diet that are hard on the body when sustained for months or years, with a significant amount of science attesting to this. A ketogenic diet has not been a natural long-term diet for human beings until very recently, especially because constantly obtaining such high quantities of healthy fats was always very difficult for our distant ancestors. Even with plentiful food available today, the ketogenic diet is still fairly difficult diet to maintain, and cutting out whole swaths of food categories is tough to handle for most people. Here's one article: https://lifespa.com/10-reasons-not-to-eat-a-ketogenic-diet-long-term/

When considering a ketogenic diet, proceed carefully and monitor your blood and urine chemistry periodically to see if your important metabolic functions are maintaining themselves well.

Look at this from a Permaculture perspective.  Permaculture Is a science based design concept.  Ketosis  is a science based biological process. Ketogenic diets were based on scientific observation that cultures that had periodic or seasonal food scarcity were healthier than cultures that had food abundance.  Differing cultures had differing coping methods but the underlying mechanism was  ketogenesis.
Because they worked ketogenic diets became a fad and fads are economic opportunity for enrapenures who's main concern is profit not health. They also became a target of others who's profitability might suffer. One of the evidences of something becoming a fad is when the words get shortened to one or two syllables because the masses are not willing to pronounce more.
Thus we have "Keto" and "permies" I accept the later contraction because it refers to the people not the science. But a new permie may insist you are not a permie unless you install a swale.  A swale is a permaculture water management tool but it is only valid if based on observation and plan it is correctly implemented only if needed.
The same hold true for inducing  ketogenesis. In the original observation when food became scarce people ate the weeds.  AS time went by they adapted by selecting more nutritious weeds and called them vegetables. The Keto fad has adapted to those that don't want to eat their vegetables. So There are a lot of products and diet recommendations that are as valid and effective as the diet fed to the rodents in the study used as the basis of the original posters cited warning study.  Not being valid to the original science they produce the opposite result from the intended.
So yes do be careful and do diligence to basically understand the science and formulate a plan to your personal culture.

When a health care client comes to my studio with their head jutted far forward, I do not take that observation and assume it is the problem. Quite often it only a symptom, problematic yes but not solved by pushing it back and causing more injury.  True health care requires observation of many factors that may be involved and discussion of the desired outcome and plan.  
 
The original post outlines a plan which may be ideal for some and teachers of ketogenic diets outline various plans which may be ideal for another.  As the original poster titled this thread be careful  and use due diligence that you understand the science behind the plan and observe the results and adapt the plan as the results indicate. Just like your permaculture plan you do not want to create an erosion problem or a stagnate rotting pond in your body.  

A few months ago I started intermittent fasting on the advice of my GP.  However, my GP took baseline blood samples and monitors my progress every few months with more tests.  (note, these tests are government-funded as is the doctor visits here.)

We've done this before with some alternative treatments I wanted to try and often the results were inconclusive or those herbs are killing you, please stop!  It's saved me a lot of money having measurable tests that we can know if the treatment is helping or not.  But when the doctor suggested the intermittent fasting, I was sceptical.  How can not eating help?  Isn't that contrary to the advice we were given with the diagnosis which was to eat constant, small meals?  

So far I've been on the 16/8 intermittent fasting which is basically eating to my natural hunger cycle.  It's also the common eating cycle for where my family comes from and I'm only the second generation away from that.  I'm very happy to just eat a big lunch and nothing else, but if I don't eat a meal in the evening, I don't feel well the next morning.  Other than making me feel better and freeing up more time in the day, I haven't had a lot of success with it fixing the main problem it was supposed to tackle.  It has, however, done a huge amount of good for a male relative of mine who has lost 25 pounds in a few months and is now testing cured of type two diabetes (although he needs one more test 6 months from now to be declared fully cured).  Apparently, men show stronger results than women.

I don't think I'm going into a keto state during my fast time.  I don't have the symptoms nor the smell.  My metabolism is pretty slow, so I'm thinking of trying longer fast times, maybe 24 hours, but I'm going to talk with my GP about that first.  I'm also thinking about stoping wheat, but again, that's something to ask about because the less variety in my diet the more likely I am to get nutritionally imbalanced.  I'm worried about going that long without electrolytes, so I hope I can have butter and broth for my meals during the fast.  I'm also worried about keto toxins building up in the system - as apparently this is something diabetics can get which damages the liver or something.  That's something else I'm going to ask my doctor about.  

When considering a ketogenic diet, proceed carefully and monitor your blood and urine chemistry periodically to see if your important metabolic functions are maintaining themselves well.

absolutely - having measurable results before and after are wonderful!  Not just Keto but any big change in diet or treatment.  

Robert Joseph wrote:I have spent over 30 years as a physician who specializes in the supervision of patients who use water-only fasting to deal with chronic disease issues. With water-only fasting, your body uses stored glycogen for fuel for about a day. If still no food is available, then protein is used for fuel for about another day. After that, with still no food available, the body wisely shifts to burning fats for fuel - ketogenesis. Ketogenesis begins after about 48 hours of fasting and continues for the duration of the fast. Metabolic ketogenesis is the body's natural adaptive response to a lack of available food.

The fundamental reason fasting is so supremely helpful for the vast majority of diseases is this: When food is not available, and is not likely to be available for some time, the body must do everything it can to survive. Once ketosis has kicked in, the body is on autopilot regarding its fuel source. Fats will be consumed as long as they are available, which is about 5-6 weeks for the average person. Ideally speaking, in order to survive for as long as possible, all systems, organs, tissues and cells should be in optimal condition. The body must quickly minimize or eliminate any weak links. That way everything can work together, optimally, to give the best chance of long-term survival to get through the current famine. So, the body gets to work, and gets to work intensely, repairing damage, removing obstructions and optimizing functions throughout the body. I have witnessed amazing and miraculous healing occurring right before my eyes on countless occasions. Our bodies are truly fearfully and wonderfully made.

My point with all of this is to demonstrate that the condition of ketosis is indeed proper and laudatory when fasting. It is a most excellent survival strategy built into all mammals. As a side effect fasting greatly helps your body heal itself form all kinds of maladies.

However, artificially creating and maintaining the condition of ketosis through a strict and measured diet for long periods of time is difficult. There are numerous aspects of the ketogenic diet that are hard on the body when sustained for months or years, with a significant amount of science attesting to this. A ketogenic diet has not been a natural long-term diet for human beings until very recently, especially because constantly obtaining such high quantities of healthy fats was always very difficult for our distant ancestors. Even with plentiful food available today, the ketogenic diet is still fairly difficult diet to maintain, and cutting out whole swaths of food categories is tough to handle for most people. Here's one article: https://lifespa.com/10-reasons-not-to-eat-a-ketogenic-diet-long-term/

When considering a ketogenic diet, proceed carefully and monitor your blood and urine chemistry periodically to see if your important metabolic functions are maintaining themselves well.

Could you explain how the traditional Inuit lived on nearly all meat and fat and were far healthier than people in "civilized areas"?  I agree that it may be difficult to eat like this, but I struggle to see how it can be deemed unhealthy when generations of people lived like this for thousands off years with no ill effects.

Trace Oswald wrote:
Could you explain how the traditional Inuit lived on nearly all meat and fat and were far healthier than people in "civilized areas"?  ...

The Weston Price Foundation and the work of Sally Fallon have some great information on this.  If you have a copy of her book Nourishing Traditions, it cites the studies.  If you don't have a copy, you can order it from your local library but it's well worth having your own copy as the book has some great stuff in it.

Some of the original studies were from the late 19th and early 20th century, so they used the language "civilized" to mean what we would call industrial-diets today.  Some of the old language has stuck around when talking about these studies which is unfortunate because the words have a different meaning today than they did then.

r ranson wrote:I haven't had a lot of success with it fixing the main problem it was supposed to tackle.

I don't know you health history, so I am not qualified to comment precisely. Generally, if your problem is a chronic one, it will require some time, and perhaps more intensive fasting for your body to heal all the layers of compensatory degenerative 'band-aids' your body has had to initiate to cope. And of course, if the primary cause of the chronic disease is found and discontinued, the problem will likely not reoccur.
As I often say, "There are causes of health and causes of disease. Practice causing health and you will have it. Stop causing disease and it will disappear."

I don't think I'm going into a keto state during my fast time.  I don't have the symptoms nor the smell.

You are definitely not into ketosis yet. It requires 36-48 hours for ketosis to kick in completely. Before ketosis, your body uses stored carbs first, then a short period of using proteins for energy. Then the wholesale burning of fats begins.

absolutely - having measurable results before and after are wonderful!  Not just Keto but any big change in diet or treatment.

Be careful about the advice of your GP. The vast majority of conventional docs have no clue about fasting, haven't done any fasting themselves, and have no clinical experience with it. If your GP does happen to have some good knowledge and experience with it, great! Best to ask him/her directly about what they know. It's all well and good to read (2nd hand) the science studies about fasting, but there's nothing like doing it yourself and supervising it for hundreds of others to really know what fasting is about.

Water fasting can sound very attractive with its many health benefits.  Indeed I used to do this quite regularly and felt I could write a book on the many improvements it made to me!  However, much later I learnt about some of its drawbacks, notably that it can slow down the metabolism.  

I would just like to further emphasise and confirm that it's best done once it has been discussed with your GP (e.g. I was told fasting is not advisable with my high blood pressure condition that developed relatively recently) and preferably with supervision - perhaps from a naturopath?

https://www.verywellfit.com/is-water-fasting-safe-4588873

Robert Joseph wrote:
I don't know you health history, ... "There are causes of health and causes of disease. Practice causing health and you will have it. Stop causing disease and it will disappear."

Yes, it's a very long and complicated history.  About 15 years ago, I was told to set my affairs in order by the end of the week, due to an infection.  It's in remission now, but it's done a lot of damage.  The journey has given me a lot of experience with naturopathic and allopathic medical systems in two countries, and I've seen the extreme ends of good and bad in both those medical styles.   What I learned is I need to take the active role in my own health.  Doctors are advisers but it's me who is taking the pills or making the lifestyle change.  If their medical advice doesn't fit with my style or I don't understand it, it is up to me to question the doctor and seek a path to health together.  

One trick I find really useful is to repeat to the doctor what I understood of the conversation.  Not only does this provide an opportunity for them to correct misinterpretation, but it shows them that I actually listened to them!  Revolutionary, apparently.  My active listening makes them more interested in helping me become healthy because they feel listened to and valued.  It's such a simple trick but it's improved the care I've gotten tremendously!  

Be careful about the advice of your GP. The vast majority of conventional docs have no clue about fasting, haven't done any fasting themselves, and have no clinical experience with it. If your GP does happen to have some good knowledge and experience with it, great! Best to ask him/her directly about what they know. It's all well and good to read (2nd hand) the science studies about fasting, but there's nothing like doing it yourself and supervising it for hundreds of others to really know what fasting is about.

This is a good point.  

GPs have a tough time of it because they have to know enough about every part of the human body and psyche to give a primary diagnosis and get us to the right specialist.  They have to be in-depth generalists and it's easy to assume they know everything!  The thing is, they are also human and the best ones I've had will admit "I haven't seen that before, but I'll go ask my colleagues in the next room if they have".

I'm very lucky in the way my doctor approaches things - the doctor knows the patients are going to try alternative treatments and doesn't poo poo them, but instead says "that's neat, I don't have any medical reason to say that will work or not, but let's monitor it and make sure it's safe to try that".  That's where the doctor first learned about fasting and saw it working for that person.  They investigated it, went to some classes, tried it for themselves, and now suggests it in some cases.

Before I started the fasting, my doctor sent me home with the suggestion of some books to get from the library - both for and against - so that I can go into this well informed.  I admit, if I hadn't read those books, I probably wouldn't have tried it as it seems crazy and contrary to what I was told by earlier health professionals.  

r ranson wrote:

Robert Joseph wrote:
I don't know you health history, ... "There are causes of health and causes of disease. Practice causing health and you will have it. Stop causing disease and it will disappear."

Yes, it's a very long and complicated history.  About 15 years ago, I was told to set my affairs in order by the end of the week, due to an infection.  It's in remission now, but it's done a lot of damage.  The journey has given me a lot of experience with naturopathic and allopathic medical systems in two countries, and I've seen the extreme ends of good and bad in both those medical styles.   What I learned is I need to take the active roll in my own health.  Doctors are advisers but it's me who is taking the pills or making the lifestyle change.  If their medical advice doesn't fit with my style or I don't understand it, it is up to me to question the doctor and seek a path to health together.

Good man! Excepting emergency situations, if one wants to get healthy, they must take the reigns themselves.
Again, I don't know your health history details, so I'll generally say that careful use of fasting, complemented by pro-active lifestyle changes where necessary, can go a long way toward healing... much more than you might guess. The healing response inherent in fasting is many times greater than normal... because it has to be to survive. If done wisely, I think you can achieve great results over a fairly short period of time.

One trick I find really useful is to repeat to the doctor what I understood of the conversation.  Not only does this provide an opportunity for them to correct misinterpretation, but it shows them that I actually listened to them!  Revolutionary, apparently.  My active listening makes them more interested in helping me become healthy because they feel listened to and valued.  It's such a simple trick but it's improved the care I've gotten tremendously!  

Again, good on ya, mate! The greatest gift we can give anyone is our full, undivided attention. It always brings the best results.

Be careful about the advice of your GP. The vast majority of conventional docs have no clue about fasting, haven't done any fasting themselves, and have no clinical experience with it. If your GP does happen to have some good knowledge and experience with it, great! Best to ask him/her directly about what they know. It's all well and good to read (2nd hand) the science studies about fasting, but there's nothing like doing it yourself and supervising it for hundreds of others to really know what fasting is about.

This is a good point.  

GPs have a tough time of it because they have to know enough about every part of the human body and psyche to give a primary diagnosis and get us to the right specialist.  They have to be in-depth generalists and it's easy to assume they know everything!  The thing is, they are also human and the best ones I've had will admit "I haven't seen that before, but I'll go ask my colleagues in the next room if they have".

I'm very lucky in the way my doctor approaches things - the doctor knows the patients are going to try alternative treatments and doesn't poo poo them, but instead says "that's neat, I don't have any medical reason to say that will work or not, but let's monitor it and make sure it's safe to try that".  That's where the doctor first learned about fasting and saw it working for that person.  They investigated it, went to some classes, tried it for themselves, and now suggests it in some cases.

Before I started the fasting, my doctor sent me home with the suggestion of some books to get from the library - both for and against - so that I can go into this well informed.  I admit, if I hadn't read those books, I probably wouldn't have tried it as it seems crazy and contrary to what I was told by earlier health professionals.  

Having spent several decades in the fasting world, I can honestly say it is the most potent, most powerful, most precise, safest, most comprehensive and most unheralded therapy in the world. All types of conventional and alternative therapies don't have much of anything positive to say about water fasting, probably because it's free, and your body already knows how to do it. No need for drugs, herbs, exotic therapies or weird remedies. Your body already knows how to fix itself, and fasting gives it the greatest opportunity to do so.

Your own body has incredible power and potential within it. Mostly we just need to get out of its way. Fasting is often said to be "the best way to do nothing." Nothing, in this case, is intelligently allowing your innate intelligence to take charge and get the job done. We simply need to stop poisoning ourselves, stop over-stressing ourselves, and learn to live a biologically appropriate lifestyle that is properly attuned to our anatomy, physiology, psychology and spiritual aspirations. Simultaneous with that, all us humans need to get our act back together and recreate a healthy natural environment for ourselves, and that is exactly what this website is all about.

I've been doing short fasts (I eat between 6pm and 9pm most days and have for more than a year) but they aren't water fasts.  I allow myself coffee with dairy during the day.  It's working well for me.

I'm going to quibble about ketosis.  My understanding is that it takes 12 hours to burn through your glycogen, and then you start burning fat.  When I started doing this, I would check my urine for ketones, and I did have some after say 15 hours of fasting.  I wasn't in full ketosis, with the "fruity" breath and all that, but I was making ketones and they were showing up in my urine.

I also don't think fasting slows your metabolism.  I really like Dr. Jason Fung on this topic.  

I've got to run, but I hope to come back and share more.

Obviously what was the case may not now be true with better knowledge.  At the time i.e. the last century, I read that fasting slowed down the metabolism which put me off continuing (and now I can't fast because I have high blood pressure!)

I have now learnt that how our metabolism is affected by fasting seems to depend on the duration of that fast.  Whilst short term fasts have been found now to BOOST the metabolism,..... 'It's well established that very long periods without food can cause a drop in metabolism.'

https://www.healthline.com/nutrition/intermittent-fasting-metabolism#section3

Julia Winter wrote:My understanding is that it takes 12 hours to burn through your glycogen, and then you start burning fat.  

It always seems to take me three full days, unless I've already been eating fairly low-carb and am doing plenty of exercise.

I tend to resort to going full keto only when I've let things slip and my blood sugars have started doing crazy things though, which generally means that I've been overeating carbs and got myself into a situation where exercise is pretty well impossible. So three days is normal for me.  I usually call them 'the three days from hell' as in that time I get really cranky and weepy and have the most terrible food cravings. Which makes life for anyone near me rather unpleasant.

I had to go through those three days very recently when my blood sugars starting yo-yo-ing and I got so low on energy that I spent nearly a whole day in tears and finally lost the ability to swallow.  I've never been that low on blood sugar before and it was pretty scary. Three days of hell, and now two in full ketosis, and I'm back on my feet getting stuff done, brain is almost functional, and all the food cravings gone.

Burra Maluca wrote:
It always seems to take me three full days, unless I've already been eating fairly low-carb and am doing plenty of exercise.

Is that three days of fasting, or three days of low-carb?  I think we might be talking about different things.  

I've never gone more than (almost) two days without eating.  As in, eat dinner on Friday, eat no meal on Saturday and then eat dinner on Sunday.  When I've read accounts of people who have done extended fasts, they do say it gets easier after the third day, so maybe you are talking about fasting?  Wow.

I need to work up the nerve to do an extended fast, and ideally a pretty low protein fast (which is what this thread is about).  I remember a cancer researcher saying that everyone over 50 should do a one week fast once a year as an anti-cancer strategy.  During an extended fast, the body starts looking around for things that can be put to a better use - autophagy, they call it.  People report losing skin tags, and not having loose skin despite significant weight loss.

Julia Winter wrote:Is that three days of fasting, or three days of low-carb?  I think we might be talking about different things.  

Three days of very low carb - 15 to 20 grams of net carbs max daily.

Julia Winter wrote:I've been doing short fasts (I eat between 6pm and 9pm most days and have for more than a year) but they aren't water fasts.  I allow myself coffee with dairy during the day.  It's working well for me.

Great. Carry on!

I'm going to quibble about ketosis.  My understanding is that it takes 12 hours to burn through your glycogen, and then you start burning fat.

In normal daily life on a varied diet, you are always burning a very small amount of fat, along with copious carbs. And even a tiny amount of protein as well. We just talk about these metabolic states in an absolute sense for clarity. The fact is that it's a fluid, overlapping situation at all times, even when fasting.
Here's a little graphic that shows what happens with fasting:

I really like Dr. Jason Fung on this topic.

Yes, he's a good one.
BTW, should anyone be interested in a supervised fast, here is a list of practitioners: http://iahp.net/refer.htm

Amy Francis wrote:Obviously what was the case may not now be true with better knowledge.  At the time i.e. the last century, I read that fasting slowed down the metabolism which put me off continuing (and now I can't fast because I have high blood pressure!)

Please do look closely into fasting for high blood pressure. It helps tremendously.

When I've read accounts of people who have done extended fasts, they do say it gets easier after the third day, so maybe you are talking about fasting?  Wow.

Yes. For probably 95% of people, appetite ceases after 3-5 days of water fasting. For the other 5%, I think it's just emotions!
And well into their fasts, plenty of people have dreams of dancing pizzas and Chinese buffets...

Amy Francis wrote:(and now I can't fast because I have high blood pressure!)

Everything I have read says that fasting lowers blood pressure.

OK, taking a break from finishing charts to address the original point of this thread:

Robert Joseph wrote: Ideally speaking, in order to survive [a fast] for as long as possible, all systems, organs, tissues and cells should be in optimal condition. The body must quickly minimize or eliminate any weak links. That way everything can work together, optimally, to give the best chance of long-term survival to get through the current famine. So, the body gets to work, and gets to work intensely, repairing damage, removing obstructions and optimizing functions throughout the body. I have witnessed amazing and miraculous healing occurring right before my eyes on countless occasions. Our bodies are truly fearfully and wonderfully made.

My point with all of this is to demonstrate that the condition of ketosis is indeed proper and laudatory when fasting. It is a most excellent survival strategy built into all mammals. As a side effect fasting greatly helps your body heal itself form all kinds of maladies.

However, artificially creating and maintaining the condition of ketosis through a strict and measured diet for long periods of time is difficult. There are numerous aspects of the ketogenic diet that are hard on the body when sustained for months or years, with a significant amount of science attesting to this.

I am in complete agreement about the usefulness of an extended fast for improving health, although this is via informed self education and not yet personal experience.  I'm a pediatrician so I'm unlikely to supervise an extended fast in a patient (although I recently saw a 15 yr old with pre-diabetes who is done growing - she had menarche at age 9 - and I think is a good candidate for an extended fast).

I'm going to take exception to the idea that a prolonged ketotic state is necessarily "bad for you."  I agree that everyone should check in on their electrolytes, creatinine, liver function, lipids when they've made a major change to their diet.  In my 25+ years of being a doctor (and advising various and sundry people, both child and adult, on food, since I also have a degree in nutrition) I've learned to be humble about knowing what will and won't work for people.  The human animal is wonderfully diverse, and people can do well on VERY different diets.

I think almost all of us know at least one person who appears to be thriving on a vegan diet.  I'm going to assume that they're getting some bugs or yeast or something to give them the B12 they need, but happy healthy vegans exist.  We have the example here in the "keto" forum of a person who is thriving on nothing but beef and water.  (I think this has something to do with a pre-existing gut problem, read Matt Walker's account for the details.)  There are people who have eaten a low carb diet for a long time and they're doing great.  

In sum, there are many different ways to feed a human.  I think it's likely that different people do well on different diets, so what works for one person won't necessarily work for another person.  And that's great!  We just need to pay attention to how we feel and try to figure out what works for us.  

a prolonged ketotic state

Something I've been wondering since I first learned about intermittent fasting but I don't know how to phrase it.

I understand ketones are something leftover or waste from burning body fat.  Too much waste in the blood can make the liver, kidneys, or other waste management systems overworked and sad.  - now this information might be old or it might be a different system altogether as the information comes from caring for an ailing relative with insulin-dependent type 2 diabetes and who liked to eat loads of fruit and sugar.  Sometimes he smelt like rotten orange and we knew he was going to be ill in half an hour or less.  The words the doctors used then was ketones (or something that sounded like it) and too many ketones was going to cause him damage to the liver or something.  

Is this the same as the ketones my body would produce when fasting?  If so, are there extra steps I need to take to keep my liver and waste management systems healthy?  This is one of the big things that is stopping me from going for the 24-48 hour fasts as I start to stink of ammonia or rotten orange if I don't eat enough carbs.

The words the doctors used then was ketones (or something that sounded like it) and too many ketones was going to cause him damage to the liver or something.  

I believe it is ketosis acidosis.  The lungs ans skin being called on to be organs of elimination

I don't have much fat on my frame to burn but I can work longer and think better when in ketosis.  What has worked for me if I have a time I want to rest, digest and rebuild I make my bread which consists of various grains and seeds ground fine and mixed with cold water, cooked for several hours in a double boiler.  If I want to go out and mow grass with a scythe for half a day I eat a high fat meal, sometimes called a fat bomb.

My body then is then content to burn fat and not send a complaint that it has run out of glucose and I need to stop and eat.