Episode 307 – The human metabolic response to chronic ketosis without caloric restriction, the blood work episode

Written by Jonathan

In last weeks show I reviewed a study about the effects of a ketogenic diet on endurance athletes and whether or not it had an effect on their ability to cycle for extended periods of time, at around 60 to 65% of their maximum capacity, if you’re interested in hearing about my thoughts and the results of that study I definitely recommend you check out episode 305 and for interests sake the name of the study is: The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation, and don’t worry if you didn’t get that I have a link to it in the show notes. I’m not going to cover the author’s conclusions or the results if the study today because I did that last week, but I did find some very interesting things with respect to blood work and basic physiology that I think many of you will find interesting and we’re going to cover those today, but since reading findings can be a little bit boring we’re going to do something different, I’m going to ask you a question, you’re going to answer it and then I’m going to go through what the study says the answer is.

In order for us to stay alive we need to get our energy from somewhere, usually this is in the form of fat or carbohydrates and our body is always burning some ratio of those two energy sources, in the case of someone who is in ketosis, they are predominantly burning fat and getting the carbohydrate required from the protein in their body, in other words the body breaks muscle down to use protein as energy and one of the byproducts is ketones, hence the name ketogenic diet.

In a standard non-ketogenic diet when most people exercise at about 65% of their maximum capacity they will burn approximately 50% of their calories from fat and 50% of their calories from carbohydrates, but when someone becomes keto adaptive the ratio is closer to 95% from fat and 5% from carbohydrates, now in this study of 5 participants 2 were able to go much further being keto adapted, 2 could not go nearly as far and one went approximately the same distance, my question for you: Do you think that every cyclist was actually keto adapted during the study or do you think some of them were not keto adapted and that’s what caused the differences on the athletes performance?
The answer:
Despite the differences in abilities all of the cyclists went from using a mix of about 50% calorie expenditure from fats and carbohydrates to almost 95% of calories from fat which is an interesting note, and suggests that everyone is capable of becoming Keto adaptive, but the effects on the endurance athlete’s ability to perform are vastly different which means not everyone is meant to move into this keto adaptive state.

This brings us into my second question for you, but a bit of background first. Glycogen is glucose that is stored in your muscles and is readily available for you to use as your carbohydrate source of energy. Your muscles are made up of slow twitch muscle fibers predominantly used in endurance activities and fast twitch fibers which are predominantly used in strength and explosive type exercises, both fiber types store glycogen for your body to use. My question – Did the endurance athletes in either test group use all of the glycogen from both fiber types? In other words at the end of this test to exhaustion, did any athletes have any glycogen aka. carbohydrate energy left in their muscles?

This is in my mind is one of the more interesting findings in this study. The muscle biopsies they took from slow twitch muscle fibres which like I said are predominantly used in endurance exercise had no glycogen left in either test group in other words it was totally depleted, but fast twitch muscle fibres still had glycogen stores in them. Which means your body knows how to differentiate between the two sources and clearly demonstrates the differences in muscle fibre use, which means if you’re exercising to burn the most calories, then it makes sense to do both steady state endurance exercise, as well as higher intensity strength and power training. To burn the greatest number of calories and maximize muscle usage. It also means if you’re an endurance athlete that you need to practice or train doing hills or resistance training, because the strength and power required to get up a hill comes from a different place than the endurance training you’re doing.

And here’s my last question – Which group burned the most total calories, the keto adapted group or the non-keto adaptive group?

I know I was as surprised as you’re going to be and the answer is…I don’t know because it doesn’t show up anywhere in this paper, yes I’m as angry about it as you are. If a paper is looking for the most efficient calorie usage it should show the difference in calories, but it doesn’t it just shows the ratios. This is really unfortunate for two reasons, one being if you’re trying to be as efficient as possible if you want to train for a race using the system that uses the least overall calories so that you can go the furthest distance then this would be really important information to have, conversely if your objective is to burn as many calories as possible you would want to know the most effective way to do that and adjust your training accordingly.

Like I said in the last episode, I can’t say whether or not a ketogenic is good or bad or whether or not it’s right for you, but what I would recommend is that if it’s something that interests you or you’re interested in trying it for a while, find a nutrition professional, a Registered Dietician or Registered Holistic Nutritionist that has experience working with people to become ketogenic adaptive and then try it for a while and experiment to see if it’s right for you.



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