Hi all, this is a really basic question but I’m wondering how dietary fat intake is related to ketone production. Obviously you want to pull fat from your body more than from dietary fat (if goal is weight loss), but does increasing dietary fat directly increase ketones? My ketones can skyrocket if I eat a very fatty meal. They are usually in the 2.5-3.5 range but can over 6 or even 7 if I eat a lot of butter and fatty things. I typically Omad by the way. Does all dietary fat consumed get turned into ketones by the liver immediately? Or is the very high fat intake just making me more efficient at producing ketones, or in deeper ketosis? Sorry I’m not sure if this question is clear, but I would love a thorough explanation of the basics of ketosis.
This is the logic and confusion I’ve come to so far: I’ve been doing keto for about a year, have read numerous books and listened to hundreds of hours of podcasts, yet I still find the basics rather difficult. In one of dr Jason fung’s books, he says dietary fat does not go through the liver, whereas glucose and proteins do. Yet ketones are created by the liver from fat (I’m guessing body fat then?). Why would an increase in dietary fat lead to an increase in ketones I’d theyre not directly related.
Does an increase in dietary fat directly increase ketones?
I don’t know if the following will answer your specific questions. It will give you good understanding of ketones.
My opinion is that burning fat is the most important thing, not how many or how few ketones and especially β-hydroxybutyrate you have drifting around in your blood. Fat metabolism is a very dynamic system and the ketone components (acetoacetate, β-hydroxybutyrate and acetone) fluctuate constantly. Don’t get attached to some numbers that will be different five minutes later.
I think this is the crux of the question.
Some fats that are highly ketogenic, called medium chain triglycerides (MCT), are absorbed in the upper small intestine and go directly to the liver via the portal vein. MCT oil is essentially entirely ketogenic. Coconut oil has MCTs. Butter and cream contain some of these fats along with short chain fatty acids, which intestinal cells use and can create ketones themselves.
Most fats also contain LCFA. Long chain fats are absorbed further down the small intestine, become chylomicrons, and go into the lymph system, then eventually make their way into circulation through the thoracic lymph duct (part of the immune system). Fat can then be used directly by the body, including muscles and heart etc. What’s leftover from that can be stored in subcutaneous adipose tissue, then released later, conditions permitting, as free fatty acids (FFA) which are what the liver will use to create glucose and ketones as needed. - [*changed this part]
At any given moment, your body is making a million tiny decisions at the cellular level. Some cells might need a little bit of omegs-3 for example and take it up from the blood. An MCT can be transformed into ketones at the same time. Other circulating lipids are stored or used as needed, with the most oxidizable ones being used first because the body prefers to store the more stable, less likely to cause oxidative damage ones. Some fat is recirculated through the liver in what some call the “futile fat cycle” whuch maintains a ready pool of available fats.
The ultimate decision of whether there is a net storage or usage of fat depends a lot on insulin levels and energy balance. A large meal will cause a temporary energy surplus. The rest of the day you’ll be in energy deficit.
The limit on ketone creation, other than MCTs, is whether or not the liver needs to create glucose due to a preceived lack of glucose/glycogen. I know that sounds strange, but ketones are a by-product of fat metabolism that converts fat into glucose when no external glucose is available. Insulin will reduce ketones. ketones themselves signal back to adipose tissue to self-regulate lipolysis, thus creating an upper limit on the amount of ketone generation.
The pool of cholesterol as a readily available energy source on keto is a tad controversial at this point though. 
That does seem on the high side for a non-fasted condition. Not harmful unless you have other issues, like high glucose or acidic blood issues at the same time.
I find elevated ketones make me a bit hyper especially when combined with caffeine. I don’t drink nearly as much coffee, tea, energy drinks any more.
Hi Carol, thank you so much for this exolanation! Do you know if any books that give an in-depth explanation of ketosis like your post? I’ve read many of Dr Fungs books, Keto Clarity and Cholesterol Clarity, and A few others, however, I would like something more textbook and in depth about how it actually works. I am also interested in learning about hormones.
Possibly this:
http://watcut.uwaterloo.ca/webnotes/PDF/MetabolismNotes.pdf
“These lecture notes, and the accompanying slides, are intended for teaching human metabolism at the undergraduate level…”
Not off the top of my head no.
I pick up bits and pieces here and there from people who know more than I do, then try to explain it to others who are curious about it. There is a topic here where Richard lays out what looks to be the basis for a future book he mentioned recently on 2KD podcast. It is from the perspective of insulin resistance/T2D.
If you’re into in-depth technical explanations, I recommend giving Peter Attia’s site a look. He generally makes a whole series of posts about a given topic with copious links.
https://peterattiamd.com/how-to-make-a-fat-cell-less-not-thin-the-lessons-of-fat-flux/
Just wanted to add a couple more references to look at how fat metabolism works - so I can find it again next time.
You can find an old version of a biochem textbook HARPER’S ILLUSTRATED BIOCHEMISTRY. I removed the link because I’m not sure if it’s an illegal copy.