Ketosis and Fat Adaptation - A Discussion and Analysis

(Michael - When reality fails to meet expectations, the problem is not reality.) #1

Let’s start with these.


PS: My hope is that some of the experienced forum members will visit this topic to address any issues and confusion presented by newbies.

Disappointed after 13 months
Disappointed after 13 months
(Michael - When reality fails to meet expectations, the problem is not reality.) #2

Corals, post:37, topic:107248
I’m googling some of the things you say to try to understand. For instance: “ketosis is a byproduct of burning fat”.

I’m back with this from Diet Doctor:
" Ketosis is a metabolic state in which your body uses fat and ketones rather than glucose (sugar) as its main fuel source.

Glucose is stored in your liver and released as needed for energy. However, after carb intake has been extremely low for one to two days, these glucose stores become depleted.

Your liver can make some glucose from amino acids in the protein you eat via a process known as gluconeogenesis , but not nearly enough to meet all the needs of your brain, which requires a constant fuel supply."

So, I still don’t understand why, when one would eat 60g of carbs per day, the main fuel source wouldn’t be fat.

Corals, post:37, topic:107248
So, I still don’t understand why, when one would eat 60g of carbs per day, the main fuel source wouldn’t be fat.

The main fuel source would be fat, no question. Burning fat can occur without ketosis. CICO diets work to burn fat. They ultimately fail because by restricting calories the metabolism gets slowed at the same time. In the followup to The Biggest Loser even after 3+ years the metabolisms of the contestants had slowed by 500 calories per day! But you can’t eat a caloric deficit forever. Thus, when they started eating more normally again they all put the fat back on and added more.

Although fat burn can occur without ketosis, ketosis can not occur without fat burn simply because ketones are a byproduct of fat metabolism. That said, all fat burn does not result in ketosis. If one eats sufficient carbs the resultant rise in glucose and insulin and corresponding decrease in glucagon prevent ketosis.

The exact amount of carbs any one person can eat but still remain in ketosis varies a bit. Most folks will remain in ketosis if they keep net carbs below 20 grams per day, which is the recommendation of the forum. Some folks who are particularly insulin resistant, may have to reduce carbs even more. Some folks can eat 25, 30 or maybe even 35 grams of carbs per day and remain in ketosis. A few claim they can eat even more, but I’d like to see some relevant data before accepting any claims of eating more than 50 grams net carbs per day and remaining in ketosis. There’s a range, sure, but I doubt its a huge range. Just my opinion.

Even though fat burn can occur without ketosis, long term fat adaptation can not occur in the absence of ketosis. I think this is due primarily to many cells/organs not being able to utilize fatty acids directly. In the absence of ketones produced during ketosis these cells/organs must use glucose. If one is eating too little carbs to produce the required amount of glucose, then gluconeogenesis will ramp up to cover the load. This in turn will ramp up insulin and depress glucagon.

Efficient fat adaptation, that is the seamless transition of extracting energy from stored fat when dietary sources of energy are absent, can not occur while insulin is busy trying to store energy in fat cells while at the same time one’s metabolism is trying extract fat from those same cells to use as energy.

‘Low carb’ meaning something less than SAD but not low enough for ketosis, or even worse in my opinion going in and out of ketosis does not result in fat adaptation. I think the reason is glycogen synthesized from ingested carbs gets in the way. When you’re in ketosis, your liver via gluconeogenesis creates whatever glycogen is required by muscles. Phinney and Volek have demonstrated that ketogenic, fat adapted high performance athletes have just as much glycogen in their muscles as athletes eating SAD. Yet they remain in ketosis and remain fat adapted. I think the reason is that when you eat glucose you get way more than you need and the excess always ends up stimulating insulin and storage. Thus interrupting ketosis and preventing fat adaptation.

(Vic) #3

Isn’t being in ketosis an arbitrairy point in a spectrum of fat/glucose metabolism.
At 80 gr carbs a day you would run out of glucose stores after a while and be in ketosis part of the day, but we don’t call it the keto diet?

Are all low carb diets a ketogenic diet ? I assume ketogenesis will be significant ones glucose stores run out.

Excess ketones are easy to meashure, makes a good point to name it keto diet when they are all day measurable.

(Michael - When reality fails to meet expectations, the problem is not reality.) #4

I don’t think it’s an arbitrary point in a spectrum of fat/glucose metabolism nor think there is such a thing. For one, fat and glucose metabolize through different processing paths. The end results may be the same: ATP, H2O and CO2, but the routes to those products are very different. Various hormones and enzymes interact and are affected differently. That’s not a spectrum.

I think Ketosis is a distinct metabolic state characterized by the synthesis of ketone bodies and their utilization by cells and organs that only results from the partial breakdown products of fat metabolism. Ketogenesis is stopped cold by relatively small amounts of insulin, which is trying to stuff glucose into fat cells and convert it to fat in the process. At the same time trying to prevent fat from leaving those same cells. That results in monumental inefficiency.

There’s no doubt that eventually when glucose and insulin drop sufficiently that fat can and will exit to be metabolized. CICO diets work, but only because they imitate starvation and if you’ve got stored fat your metabolism is going to use it however inefficiently to prevent death. It will also utilize muscle and bone if it has to. Think about this. After eating SAD for years or decades how long did it take to burn out sufficient glucose and glycogen to start to burn fat? How long did it take to start to synthesize ketones? A day? 2 days? Whatever it took, you’re just putting your system through that process over and over again on a daily basis by not keeping the carbs low enough to maintain consistent ketosis. You’re not going in and out of ketosis smoothly after every meal. You’re not fat adapted. In my opinion.

(Michael - When reality fails to meet expectations, the problem is not reality.) #5

Amy Berger, whom I admire greatly and read extensively, disagrees with me about whether you can be ‘fat adapted’ and non-ketogenic. She thinks you can be. Here’s her explanation:

(Bob M) #6

Some of us get very low ketones, so the typical “ketosis = 0.5mmol/l of BHB” doesn’t work.

I started and restarted Atkins many times, back when I thought I needed carbs for exercise. It took a good 2-3 weeks for the initial transition, and more weeks for exercise. That is, exercise did not feel as good…for a while.

As for how many carbs “kick one out of ketosis”, I’d bet this is variable. Someone like me, LC/keto 7+ years, I’ve gone on vacation (pre-pandemic) or had days of high carb (birthdays, anniversaries), and have been either shocked at how quickly I got back into ketosis or wondered whether I went out.

In other words, if you’ve been keto for a month and have a weekend of carbs, it might take quite a while to get back into ketosis. For me, I can either not go out or get back in a few days or less.

And activity level has a role to play here, too. If you eat high carb for two days, go on low carb, but run 10 miles, you might get right back into ketosis. Or if you eat two high carb days while riding your bike 60+ miles a day, you might never get out of ketosis.

(Bob M) #7

Thanks for providing me what I’ll read at “lunch” (my first meal of the day) tomorrow.

(Bacon is better) #8

No, because it’s not a continuum. It’s on or off.

The threshold of carb intake will vary according to our degree of insulin resistance, but the key is how much insulin gets secreted in response to the carbohydrate we eat. Someone who is very insulin-resistant will have a much greater insulin response to the same amount of glucose in the bloodstream than will someone who is more insulin-sensitive. Therefore, the insulin-sensitive person is more likely to remain in ketosis, because their insulin level stands a better chance of remaining below the threshold. But once we rise above the threshold, ketogenesis stops, fat gets trapped in our fat tissue, and the body switches to metabolising glucose.

(Vic) #9

Ok thx,

Here is a another question.

When we are in ketosis, for a long time, well fed, catabolic state.

Our cells will be full of energy.

Suddenly we are force fed 5 bananas.

Would we not be very insulin resistant ? After all our cells are full and will resist more energy from the glucose.

(Bacon is better) #10

Not at all. The cell’s response to insulin is a reaction to its previous exposure to insulin and has nothing to do with fatty-acid metabolism. Insulin resistance occurs when the cell has been so stimulated by insulin that in order to defend itself from further stimulus, it reduces the number of insulin receptors on its surface. Fat cells do this, for example, when they are full of triglycerides and don’t really have room for more fat.

This starts a vicious cycle in which the pancreas starts pumping out even more insulin to keep forcing glucose into cells and get it out of the bloodstream, and cells keep reducing their insulin receptors to keep from getting overwhelmed.

After we cut our carb intake, this over-secretion of insulin continues, but eventually the pancreas stops over-secreting insulin in response to what little carbohydrate we do eat, and the cells of the body start allowing insulin receptors to return to their surface. This means that it takes less insulin to deal with glucose, and the result is a beneficial cycle that eventually results in a return to insulin sensitivity, if we stay off the carbohydrate.

To understand all this, remember that too much glucose in the blood (hyperglycaemia) is dangerous and can even cause death. So the insulin response is like the fire brigade showing up to deal with a fire. But as you can imagine, having firetrucks always showing up at your door gets annoying after a while. As we stop paying attention, they start sending more and more fire trucks to force us to deal with the emergency. But stopping the emergency conditions (in this case, too much glucose) is the real solution to the problem. That way everyone can go home and relax! It’s important to have fire trucks, but no one wants too many of them hanging around all the time.


Interesting thread, I hope I can learn things I always wished to know… You guys explain things better than too-scientific-to-me articles and I never had the patience for long videos.

CICO works because the energy must to come somewhere. It’s quite different using a small and a huge energy deficit, the latter is usually harmful starvation, the first isn’t and shouldn’t significantly harm the metabolism though it happens to some…

Low-carb (but not quite keto) is interesting, I’ve read so many things about it and part of it was clearly untrue. It works wonderfully for so many people. I felt great eating up to 80g net carbs (and zillion total, probably). Keto wasn’t much better, just harder, it helped nothing with fat-loss but I unlocked fat adaptation and needed it before I managed to go lower where serious things happened.
Why do we have different significant limits I wonder. My ketosis carb limit (around 40-45g as far as I could tell) doesn’t feel significant. 80g and 10-20g are the important limits, I feel very different when I cross those. What the hell does my body do? Shouldn’t ketosis be the special thing (it is but I don’t really feel it, barely anything changes)? Or carbs are powerful enough to offset that? I know I have a special relationship with carbs, they are little gremlins doing weird things.

I am curious about the 5 bananas thing… As far as I know, our body minds its own business, enjoying its physiologically insulin resistance and it gets shocked suddenly getting all the sugar. It can explain why many people feel bad after eating a lot of carbs when being in ketosis originally.
But some people keeps feeling just great when they do that. If I get a properly sized sausage (100g fat and lots of protein) afterwards, I am fine. Carbs alone and I will be miserable. Why can a bunch of fatty protein prevent bad feelings this effectively? I always feel the irresistible pull to eat more fat when I eat carbs and it mitigates the problems (I never feel as good with carbs as without but I rarely feel unwell). But if I try to eat just a bit of sugar all alone (~20g grapes did that to me), my body tends to complain.

(Bob M) #12

There may be a few reasons why you experience this. If you’ve been low carb for a while you’ll develop “glucose intolerance”. That is, your blood sugar will go higher than it would without the intolerance, if you eat carbs.

The other thing is that you might get a low blood sugar value after eating carbs. That almost always causes bad effects (e.g., poor mood. hunger, restlessness, etc.). Check out the red part of this curve, after I had two slices of ice cream pie.

I’m sure I was hungry after that, but I went home after this.

If you DO want to have carbs, such as bread, the best thing to do is to eat it last. Eat meat/vegetables first, bread last. Supposedly, this causes a much lower blood sugar response than bread alone or bread first. (I did not test this when I had my CGM, as I ate bread less than a handful of times in a year; maybe twice.) I learned this from Gabor Erdosi. If Apple or Samsung do come out with a CGM watch, this is on my list of things to test.

And, of course, you could just be intolerant to what you are eating.

(Bob M) #13

@amwassil With what do you disagree in those Tuit Nutrition articles? To me, she described my experiences exactly.

Though I do find it a bit odd she had never used BHB meters. But when I started using them, the strips were $5/each. So, I could see the reluctance. Even now, with the strips being $1/each, to do any real testing, it’s costly.

At one time, I was testing before and after exercising and throughout the day. This makes you realize how fickle they are and your body is with ketones. I’d get some pattern going (usually, ketones go down for some exercises), and then find a test that broke that pattern. This is why I stopped using them. Though I may get some just to see what’s going on. Am I still super low? (I think the answer is “yes”, as I am still using my Ketonix breath analyzer, and my breath ketones are very low.)


Thank you for clearing the thread. I was feeling so bad for hijacking someone else’s!

You assume anyone eating carbs, say 60g, produces a lot of insulin to deal with that. But that’s not so. Not everybody is insulin resistant. Many people won’t see any bump in insulin to deal with a small carb load like that. I’m not talking about myself, unfortunately.

You’re also assuming if one is not eating carbs, insulin is low. Now, I’m talking about myself. I can fast 48h, run on day 1, say 1h, mountain bike on day 2, say 4h, before eating. Been there, done that. I measure BG before this start, it could be high, even though I was having very little carbs before the fast, say, below the 20g. After every bout of exercise, my BG goes up. Up! Recently, after fasting for a blood test, my FBG went from high 90s (after over 12h fast), to above 110 mg/do, while still fasting, hours later. My insulin? 61!

So, eating carbs doesn’t mean high insulin for someone (unfortunately not me) with good insulin sensitivity, just like not eating carbs (or anything for that matter), doesn’t mean low insulin for someone (unfortunately, like myself) who has some degree of insulin resistance (not to the level of diabetes).

But when people talk about these issues, they assume everybody is the same. We aren’t!

You also assume (sorry if I’ve misunderstood) that one needs the stored fat from fat cells to function. What about fat eaten? I’m asking to be sure I understand.

Also, eating so and so carbs doesn’t mean one is cutting calories. One can be maintaining weight and only playing with macros.

It’s my case. I’m happy with my weight. I was keeping my weight before, when I was low fat. I am keeping my weight now, that I’m (very) low carb. The amount of calories? About the same. No magic weightloss (and I don’t mind). Why I do it? Low carb food tastes better AND I want to try increase my insulin sensitivity, hoping that’s possible, but not yet convinced it is.

Just for info: I’m asking questions, just because I’m curious and I want to understand. I have no doubts this WOE is better for me (because of insulin sensitivity issue).

(Bob M) #15

This happens to me too, especially in the morning:

I have months of data that look exactly like this. (Multiply by 18 to get US units.)

My blood sugar also goes up after exercising. I believe (though don’t know) that it’s your body’s way of replacing glycogen and/or preparing for the same.

The insulin number is more concerning. That should be closer to or below 10. How many times have you had your (fasting) insulin checked? What were the results?

Unfortunately, until we have a home insulin meter (even with strips), a lot of these questions/issues can’t be answered. I generally have insulin below 10, but have had as high as 33, for reasons not clear to me.

(Edith) #16

@Corals, I copied this from one of your posts on the previous thread.
You did say you only eat about 1200 calories a day. That is why I mentioned low food intake possibly being a cause of your low energy.

"Protein varies, around 110g/day. Fats, about 130g/day.
110x 4= 440 Kcal
130 x 9 = 1170 Kcal."


I love when you share your data! Love it!

Unfortunately, it was only measured once.
FBG was 106 mg/dL and insulin was 61.4 pmol/L. A1c 5.5 %. I’m so disappointed with my insulin! I hope this is something that can be changed, or at least that won’t get worse if I eat very low carb.


Except if someone is like me. I get unwell if I don’t eat fatty protein after any carbs I eat. If I just include a lots of fat, I may get away with it but alone in the end? Sugar poisoning and hunger. No way I ever eat carbs without fatty protein afterwards again…

And I always find these… separating advices vastly unnatural in most cases. We don’t eat first meat and then bread. We eat things together. I can eat almost anything separately but the people I know eat everything together. Who eats bread alone and why? The bread lovers I know wouldn’t eat it alone, no matter what.
(But I don’t understand people eating the toppings of pizza either, it’s wasteful and makes no sense to me as a hedonist either and still, people do it. Odd.)

(Michael - When reality fails to meet expectations, the problem is not reality.) #19

I don’t disagree other than I wouldn’t describe ‘fat adaptation’ as simply the ability to metabolize fat. My response to that is: so what? Maybe I’m just arguing symantics. But my view is that simply metabolizing fat is not the issue. Anyone can metabolize fat thanks to 3+ million years of hominid evolution. Even obligate herbivores actually metabolize fat - they eat cellulose to feed their gut bacteria which in turn ferment it into short chain fatty acids, which is what the herbivore actually uses for fuel.

I think the issue is one of efficiency. CICO proves you can burn fat at the same time that insulin is trying to stuff glucose into the same fat cells. But to me that sure looks like one of those “what’s wrong with this picture” sort of things. So I don’t describe that as being ‘fat adapted’. When you get insulin out of the way by remaining consistently in ketosis your metabolism utilizes fat much more efficiently and thoroughly simply because it’s not working at cross purposes. I call that fat adapted. While fat adapted by my definition, your metabolism also produces and processes the glucose you need without interfering with fat metabolism. Thus, I conclude that real fat adaptation requires ketosis.

This also bears upon the issue of so-called metabolic flexibility. Eating carbs to the point of stopping ketosis is not flexibility - you just stopped the efficient metabolism of fat. What’s’ ‘flexible’ about that? Ketosis is the actual state of metabolic flexibility because you’re metabolizing both glucose and fat efficiently. And, yes, I know the official definition of metabolic flexibility and think it’s nonsense.

(Bacon is better) #20

Actually, insulin goes up whenever we eat. If it didn’t, we would starve to death. Fat raises insulin secretion the minimum necessary for survival.

Protein raises insulin to some degree. In a low-carb setting, the increase in insulin is matched by an increase in glucagon, the insulin/glucagon ratio stays low, and the body remains in ketosis. In a high-carbohydrate setting, insulin goes up, and there is no matching increase in glucagon.

Carbohydrate, being pure glucose, raises insulin the most, because too much glucose in the bloodstream is toxic and must be dealt with.

There is no way to measure your insulin level at home, because it require radioassay equipment unsuitable for an inexpensive home metre.

The question is how much carbohydrate someone can eat without raising their insulin/glucagon ratio to the point where it shuts off ketogenesis in the liver. I don’t know any way to predict this, because everyone’s metabolic situation is different. Given the same amount of carbohydrate, an insulin-sensitive person will have a lower insulin response than an insulin-resistant person. But that amount of carbohydrate, whatever it is, might still be enough to shut down ketogenesis, even in the insulin-sensitive person.

Most of the recurring discussions on these forums, about how much carbohydrate people can get away with eating, sound very much like the sorts of things heard at A.A. meetings from alcoholics who are trying to find a way of staying sober without actually giving up alcohol. Unlike those alcoholics, we are fortunate that our drug of choice, carbohydrate/glucose, can safely be eaten, if the dose is small enough; we are not required to go full-on carnivore in order to get the benefits of ketosis. It is hard to accept, however, that there actually is a limit, and that limit is fairly low.

The alternative to cutting carbohydrate intake and increasing fat intake is the Kempner rice diet, which is extremely high in carbohydrate and extremely low in fat. It does work, and some people on the diet permanently reversed their Type II diabetes, but it is apparently a hellish diet to stick to, and patients (so the story goes) actually begged Dr. Kempner to whip them, so that they could stay on the diet. (Yes, he obliged them.)

I think I’ll stay keto, thank you very much. Bacon, yum!! :bacon::bacon::bacon: