Metabolic Characteristics of Keto-Adapted Ultra-Endurance Runners

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

@Mavro posted this link in another topic. I think it’s a very important paper so created this topic to preserve it for posterity. :heart_eyes:

If you think top athletes require carbs/glucose, please read the entire study before posting. Thanks.

Peak fat oxidation was 2.3-fold higher in the LC group (1.54 ± 0.18 vs 0.67 ± 0.14 g/min; P = 0.000 ) and it occurred at a higher percentage of VO2max (70.3 ± 6.3 vs 54.9 ± 7.8%; P = 0.000 ). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21 ± 0.02 vs 0.76 ± 0.11 g/min; P = 0.000 ) corresponding to a greater relative contribution of fat (88 ± 2 vs 56 ± 8%; P = 0.000 ). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (− 64% from pre-exercise) and 120 min of recovery (− 36% from pre-exercise).

Spike in blood glucose meter reading
Appetite Suppression and Hypoglucemia
(Bunny) #2

Only if you don’t want to burn up your muscles and you have no body fat (you quit sparing muscle), it (carbs/glucose) probably would be required unless you got lots of fat on-board to burn? Or you eat enough protein to replace the glycogen via gluconeogenesis?

Phinney nor Volek (the researchers in the study your citing) know exactly what’s being used for fuel “hard to say” which they plainly state on the Virta Health website?

One thing is for sure you will never use 100% ketones or fatty acids for fuel there is just not enough of it, it’s just not happening chemically, electrically or mechanically as muscle tissue is designed to store glycogen for energy and to think otherwise is magical thinking?

There is also a paradox to this, being Phinney & Volek are advocates of meat and fat for fuel? Dr. Peter Attia demonstrated in his own N=1’s eating resistant starch is where you truly get BHB from and when your body truly kicks-in butyrate or ketones for fuel because eating only meat and fat kicks-in glucose/glycogen for fuel?

This is also demonstrated in people and cultures who eat high starchy diets; they run faster and longer than anybody in the world and beyond the threshold of even an Olympic athlete?

Why is that? Because they make and produce there own butyrate or ketones for fuel? Rather than constantly depending on an exogenous source (animals)?

And of course the meat and fat advocates are going to throw a temper tantrum jump up and down and throw themselves on the floor and convulse into make believe seizures because technically resistant starch is a CARB…lol


Serum glycerol spiking really high during exercise in the ketogenic group is really interesting. Glycerol is what’s being converted into glucose. Page 106.

Plasma glucose is relatively stable in the ketogenic group. Page 107.

They did intake carbs. Some more than others but page 108 is interesting regarding muscle glycogen.

(Give me bacon, or give me death.) #4

It’s a sign of lipolysis, the breaking down of triglycerides into their component fatty acids.

(Bob M) #5

Zach Bitter (super ultra-marathoner) still takes in some carbs while running. I’m not sure about how much he takes during his day.

And realistically, 80grams for as much as these people are exercising is nothing.


This too. Component fatty acids and glycerol. The point I was making is that nobody is an exclusive fat burner or carb burner but being ketogenic will make it much easier to have optimal glycemic control because the glucose is made as needed from the glycerol.

(Michael - When reality fails to meet expectations, the problem is not reality.) #7

For what little it’s worth so far, my Lumen seems to confirm that. My CGM experiment indicated that I have normal glucose. Being continuously in ketosis and consuming less than 15 grams of carbs per day, I had expected to see very low glucose. Not so, perfectly normal. That glucose is going somewhere and the Lumen picks it up as ‘carb burn’.

(Bob M) #8

I think this is why high exercisers (meaning keto and exercising “a lot”) can have higher glucose and high LDL/TC (energy model).

For me, when I exercise, I get higher blood glucose, and if I follow that by working on the house (essentially exercise), then my blood glucose stays high. Or if I just work around the house, my blood sugar is higher.

I think that’s the way the body responds, which I think is to replace glycogen for instance. (Otherwise, how does it get replaced?)

And you look at someone totally crazy like Shawn Baker, he has very high blood sugar, even though he eats mainly steak. Why? It’s to fuel his insane workouts. And I mean insane – watch his videos sometime.

(Michael - When reality fails to meet expectations, the problem is not reality.) #9

Lessons from Low Carbohydrate Athletes

Perhaps the situation perceived as most challenging for someone on a ketogenic diet is the ability to maintain glucose/glycogen reserves with prolonged, high intensity exercise. For a greater part of the last century, the accepted paradigm has been that one’s initial muscle glycogen is positively correlated with the ability to sustain endurance performance during moderate-to-high intensity exercise¹²,¹³. However, given that even with ‘optimized’ muscle glycogen obtained by using a carbohydrate-loading diet strategy, an endurance athlete has a peak total body glycogen content of only about 2000 kcal. To attempt to simultaneously train the muscles to use more fat and reduce one’s dependency upon glycogen in order to extend performance creates somewhat of a metabolic oxymoron. This is because very high insulin levels induced by carbohydrate loading actually suppress adipose fatty acid release and oxidation.

(Rjrnj1 ) #10

You know, atomspacebunny, everything you wrote was quality until your snarky comment at the end. Now I’ve got to read this information with a grain of salt. Pity.