Hi,

thanks for that still great note. I undersant the ketosis state I call now "the bear diet" (meat, fish and berries). But i am wondering about reducing carb for stillness of mood and energy level for an average active thinking and training guy.

I am confused by the words : If we have excess glucose in our bloodstream, our muscles will burn it first, because it’s toxic. But eventually we run out of glucose, and that’s when our bodies need to switch over to beta-oxidation—burning fat. The ability to switch back and forth between the two processes is called “metabolic flexibility” in the scientific literature.
Because the word "switch" make me thin that beta_ox of fat and glycolis won't occur in the same time. this would induce that as your brain require glucose, if you couldn't have beta_ox while glucose in blood from carbs then you have to use gluconeogenesis to feed your brain.

I want to burn Fat from food as a first source of energy when possible and feed my brain from carbs from food not from gluconeogenesis. Indeed i guess that gluconeogenes is expensive in terme of energy to get glucose. you confirm it is possible?

Very enlightening ! Weigth loss is my main goal for now and I am still researching this whole healthy lifestyle deal (having eaten practically exclusively trash since 2005 and paying for it now). This has put me substantially closer to favoring paleo over vegan or any other lifestyle. I am deliberately using the phrase "lifestyle" here, because I don't want a fix or a short-term solution. I want to redefine my body and my self (however cliche that sounds ;]).

I have only one question though : How exactly would I measure my current RER level ? Is there an easy way ? I couldn't find anything on this topic here and google also didn't prove to be of use.

Very good read J. Thank you

This is surprisingly the first time i have seen this article from you.. not sure how I missed it.

At Primal North we have coined at term "Low Carb Limbo" which describes the person eating to few carbs to support their daily activities, but to many carbs and protein to obligate the neccessary blood ketone level that will have your muscles using ketones preferentially over glycogen.

This misguided approach will eventually cause all sorts of issues and it is why a blood keto meter is not optional but essential for anyone practicing athletics along with a ketogenic diet. It is a perpetual "low carb flu" as your energy demands are not met with carbs, and not met but having high enough blood ketones.

You are also about the only person I have seen outside of Phinney and Volek who correctly makes a distinction between fatty acid oxidation and keto adaptation. We continually see the term "fat adapted" and people assume that means they are keto adapted. Of course they are not and this assumption hurts them as they simply shut off all carbs, up fat, and continue to exercise without adapation period.

I submit in my "Low Carb Limbo vs Keto Adaptation" article that all humans are already "fat adapted" and able to oxidize fat when carbs are unavailable. That what we mean by "Fat adapted" is that we have actually worked on the ability of that system to ramp up as needed to much greater amounts than the average high carb eating member of the sedentary general masses.

Anyway your article has me rambling, it was a worthy read. Thanks.

Glucose is an anaerobic fuel, not aerobic. Its use as a cellular fuel predates the existence of multicellular organisms. (Insulin, in fact, is one of the oldest hormones on the evolutionary timeline, and can be found even in simple worms.) There are two types of fuel-burning that can be done by cells in the absence of oxygen: anaerobic respiration, and fermentation. I'm not a cell expert but from what I can tell from a cursory search, eukaryotic cells (cells with nuclei) tend to use fermentation when burning glucose. Glycolysis can happen in the presence of oxygen, but never *uses* oxygen. Cancer cells tend to favor glycolysis, in fact, because they tend to be unusually sensitive to free radicals and oxidative stress, so they do what they can to minimize contact with oxygen.

This is a really useful post for me, though. One more piece of my personal puzzle because there is a hell of a lot of type 2 on my mother's side and I had trouble with obesity early in my adult life. It seemed to be in response to hormonal changes, but still, certain dietary choices seem to have a better track record with reducing it.

Very informative. I'm assuming you suggest eating the required carbs with complete fats and proteins because of fats sugar spike dampening properties?