Ketone-levels keto vs. fasting, why the big difference?

(Sascha Heid) #1

I don’t understand why there seems to be such a massive difference in ketone-levels between a standard keto diet and an extended fast.
On keto 70-80% of calories come from fat, be it body-fat or food-fat, both will end up as ketones in the blood, right?
During an extended fast i’m guessing 95% of calories come from body-fat (after the transition-time of 3-6 days).
So we have ~75% vs. ~95%, that is not a big difference, but yet the ketone-levels on an extended fast rise up dramatically. They are not increasing by 30%, they are multiplying.
Why in the hell is that?

(Bart) #2

less insulin, so the liver produces more. Even eating keto when your body produces insulin it will slow ketone production, even if the insulin is raised from a non-carb food like protein.

(Bart) #3

It is talked about in this paper, I believe chapter 4 (the link starts on chapter 3)

(Sascha Heid) #4

I understand why there is a difference, but not the magnitude of it.
If my ketone-levels rise by a factor of 4 during an extended fast, then my energy-utilization from fat has gone up by a factor of 4 as well. If this is true then i did only get 25% of my energy from fat previously, when i did keto.

(Bart) #5

That link I supplied talks about ketone utilization and also Free Fatty Acids, it speaks about nutritional ketosis vs fasting and starvation. It is a good read. I recommend reading it. If you do not have a derranged metabolism you will see higher numbers than many with one. If I am eating keto, but a couple of meals a day my levels are 2-4, they jump to consistently being 5.5-7.1 when I fast, even 24h intermittent fasts. Right in the levels the paper I linked to says they should be. When you are eating keto and not fasting some of the fats in your diet are being used as energy, when you are fasting your body has to breakdown more fat in your cells for energy.


I know that this is a relatively old thread but I’m so happy to have found it. Right now I don’t have a way to measure ketone levels but I’m really happy to see that levels jump (or can jump) in short fasts.


Excellent read. Thanks.


As I read this pdf, it seems to indicate that consumption of protein can be reduced once an individual is fat adapted. To my knowledge this is the first time i’ve ever heard of this and it makes sense to my experiences.

While on Keto, i’ve tried to follow my own saying of “when in doubt, add more fat” - now I can see that being even more applicable as our bodies change what they use for fuel.

Excellent first read and i’ll have to re-read after a few weeks allowing more space to absorb a few more understandings.

Thanks again for the upload.