PRESS RELEASE
I have written an article in Medium that I have completely forgotten about mentioning here. Bad girl… well, it is better later than never. Shortly after I published that article and it went viral, it was republished by Marika Sboros on her website with a beautiful header image that I love to look at. Whichever you prefer to read, just read it.
What’s All The Fuss About?
We often hear that glucose is the human primary fuel and ketones are the secondary (backup) fuel for those times when glucose is not available. But is that really true?
Thinking that glucose is primary is nothing short of suggesting a dentist is primary because that is the mandatory “first thing” (primary) you need to do if you have a tooth ache. It is not primary; it is very urgent. If you had a choice, and had no tooth ache, visiting the dentist would be the last thing on your list.
And so it is with glucose versus ketones and also versus alcohol, for that mater, as one of the readers noted in a comment. Indeed, alcohol is also a fuel, and it yields 7 Calories per gram! Recall that glucose provides 4 kcal and fat 9 kcal, so what is the order of fuel-burning preference? 4, 9, 7 or 4, 7, 9, or 7, 9, 4, or 9, 7, 4, or 9, 4, 7, or 7, 4, 9? What exactly is the process based on which the body decides which fuel it uses first? Is it by how much energy it can get from it or by some other magic?
The Fuel Order Question
This is not at all intuitive. How does our body choose which fuel it should use first? From the perspective of energy output, our body should definitely not choose glucose first since per gram the output is only 4 kcal, the smallest usable energy possible to be gained from any of the fuels. From the perspective of energy output, the first choice would have to be fat.
However, just like visiting the dentist provides a huge payoff when there is urgency, but not at any other time, perhaps our body is smart and chooses its fuel based on the urgency by which it must be removed from the body with minimal negative consequences. And this, indeed, is what is happening.
Urgency & Priority vs Primary
And here is the important part. The human body is a smart one. It had millions of years in which to figure out the order via evolution. It picks based on an order of urgency, and priority will be given to the most dangerous of fuels, which have negative consequences if they remain in the body for long. The body will use the dangerous fuel first over fuel that can be stored without negative consequences.
So what will the order of preference be in burning the 3 fuels?
Alcohol, glucose, and then fat (aka ketones).
And this is in order of urgency and not based on which is primary. In the article I only discussed 2 fuels and I added now alcohol as the 3rd. Here is a quote from the original article that explains the two fuels:
Few professionals, even within the field of nutrition, realize that ketones are not our backup fuel. Ketones are not any more backup than glucose is the primary fuel. The human body has no primary or backup fuel: it has two fuels. I presume that the urgency for glucose use — meaning the urgent removal of glucose from the blood — is misleading and makes people think that if the body switches to using glucose the moment it is provided, it must be its primary fuel. But this is a mistaken argument, which assumes that the first task that has to be done is the preferred task. It is true that when we add glucose to our blood by, for example, eating carbohydrates, the body must immediately switch to remove that glucose from the blood.
The maximum comfort level for glucose in the blood is 99 mg/dL (5.5 mmol/L) and if we eat carbohydrates such that this is exceeded, it is literally an emergency and the body must remove it from there. Too much glucose in the blood for extended time is toxic. However, having to remove glucose immediately does not make it into the primary fuel, it just makes it into an urgent task.
Had I thought of adding alcohol into the original article, alcohol would be the first fuel used because it is the most toxic, glucose as second because of its toxicity, and fat as third because it is not toxic at all.
Children Are in Ketosis
In the original article, you will find discussion on Cahill’s landmark article (1), which you may or may not be familiar with. His work is focused mostly on ketosis during starvation. By starvation, understand “fasting” in modern terms. Babies, for example are in ketosis all through their early teenage years–as per Cahill–even 20 minutes between feeding initiates starvation responses in babies. But there are articles showing that the fetus is also in ketosis in the womb, where there is no starvation, and babies remain in ketosis even after eating–clearly no starvation there. So there is more to ketosis than meets the careless eye.
In my Facebook migraine groups (here and here) the migraineurs measure their blood glucose and blood ketones over a 5-hour postprandial period, and post their data for my analysis. I usually graph this and discuss the course of action to take in nutrition. Many moms and dads are in the groups for their children, and the children also submit their 5-hour postprandial tests (also fasting and pre-meal).
It is fascinating to see that every single child , so far through age 16, is in ketosis even after a breakfast containing fruits and milk.
I suppose few people have the same opportunity as I have in being able to measure the blood ketones of various ages of children for five hours postprandial plus fasting and pre-meal measures. And so ignorance is bliss…
Thus, while today in most countries around the world any type of food is just a short walk/drive away 24/7 and we need not experience hunger and starvation, our children are still in ketosis 24/7. Shouldn’t that tell us something about the importance of ketosis?
Conclusion:
With all due respect, I disagree with glucose as the primary human fuel. Glucose is not primary or secondary or any-ary. It is a fuel that is urgent to be used up as fast as possible and so it gets used first (after alcohol) but not because it is primary but because we need to get rid of it faster than fat.
Sources:
1 Cahill, G. F. Starvation in man. N Engl J Med 282, doi:10.1056/nejm197003052821026 (1970).
Comments are welcome, as always, and are moderated for appropriateness
Angela
Clueless Doctors & Scientists 
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So why do we have so many obese children?
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J great question! There are more than one reasons for this. One of them is what the mother ate during pregnancy. There was a bit of a discussion on this on twitter the other day. While insulin doesn’t cross the blood barrier of the placenta, glucose does. When the pregnant mom-to-be eats a high-carbs diet, the fetus must release correspondingly high insulin. This is one reason why moms who have gestational diabetes and consume a lot of carbs to maintain blood glucose at a certain level via carbs, have amazingly large/overweight babies at birth.
Another reason, is of course, what the babies are fed after weaned from breast milk. My younger granddaughter was born 4.5 years ago and I still remember the struggle my daughter in law had to go through to provide any food to that baby without rice flour/starch, corn flour/starch, wheat flour, cereals, sugar, and alike. There is simply no general and affordable baby food out there without all that trash–including vegetable oils. All babies are weaned to skim milk or milk substitutes–the stupidest suggestion. Juices are recommended–they are very high fructose and cause major issues, including non-alcoholic fatty liver disease in a very short time. So, children, at a very young age–even at birth–can be very obese based on food–from mom or by eaten by the baby directly.
My granddaughter ended up eating home-made foods–basically eating what we ate, including meat, only blended to smooth–and whole fat milk. And she is not obese.
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What a fascinating article! Thank you.
Amazed to read that children are in ketosis the whole time. What about kids that eat junk food the whole time? For example, sugary cereals and bread for breakfast, coke and hamburgers on white bread with chips/French fries for lunch, more carbs for snacks and evening meal with sugary dessert. Surely they can’t be in ketosis too?
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Great question Jane. They will not be using ketones while the glucose is being used up but after a certain hours of not eating glucose runs out, and ketones return. Children have such fast metabolism that ketones are permanently “on call”. Every single night they go into full ketosis since they are not fed for at least 8-10 hours.
In my original article on Medium (https://medium.com/@angelastanton_25177/our-kids-are-in-ketosis-d03e336c9bdf) I have a graph from Cahill, the leading scientist at the time on ketosis. That graph shows how long of not eating it takes to get into ketosis for all ages and both genders.
This graph is not specific to any special eating way, so it can be all sweet junk food for our purpose. Children, according to Cahill, between ages 2-4, for example, are back in ketosis burning ketones after about 2 hours of not eating.
Even adults, when preparing for a blood test and fasting for 10-12 hours, females are producing ketones by the 10th hour; males a little later, no matter what food they eat. All labs have a ketones of 0.3 mmol/L allowance for such blood test as “normal” as a result.
We have to accept that ketones are permanent features of our lives at every age. 🙂
Angela
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Yes great stuff and should be nailed to the forehead off all those dieticians who tell us “we must eat carbs for energy” and insist on weaning children onto cereal and fruit.
That advice ruined my life for fifty years. I see it still ruining others’ lives. Typically people who visit the local nature reserve start off in the cafe then walk round eating chocolate bars and drinking energy drinks. They are often fat because their ketosis/fat metabolism has been stalled by the constant carb input.
Meanwhile I have my typical breakfast of a thickly buttered oatcake with smoked salmon and a couple of cups of coffee then walk around the whole place and don’t eat again until maybe late evening because I can access and metabolise all the food from the previous day’s meal(s).
I feel their pain because when I used to diligently “base every meal on healthy whole grains” I couldn’t walk more than two or three hours without carbing up or I would fall over.
Glucose is like fast burning rocket fuel. Fats and ketones are like diesel. Only one explodes.
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I would say fats and ketones are solar energy because they are cleaner or nuclear because they provide way more energy than glucose or alcohol but without combustion or polution. 🙂
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One thing I’ve seen that makes a lot of sense – we only have one hormone to reduce blood glucose – insulin – which also has a bunch of other actions. We have several to increase glucose – glucagon. cortisol, epinephine etc. Since some (but not many) tissues require glucose and we can manufacture all we need from protein and to a lesser extent from fats (glycerol backbone of triglycerides) we obviously never evolved on a high carb diet. Tell that to a dietician and watch her head explode . . .
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Precisely!
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Re: “…….and watch her head explode . . ..” Time to go out and tell her that, I’d say.
Um……. all dietitians are female?
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No, of course not. Perhaps Chris’ nutritionists are all female… but that’s OK. This blog is not politically correct in any sense of the word. 😉
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The worst ones are. (runs away)
Actually some of my better doctors have also been female. Make of that what you will.
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I have only met one nutritionist and that was only to have her refer me to the ketogenic diet group at this medical institution (Kaiser) that has one for epilepsy. Since I had no epilepsy, I had to be referred by a nutritionist. As she was letting me into her office, she opened up a folder of what she planned for me: 350 gr carbs a day… I made her close that folder right away and told her to trash it… lol. The person I met there about nutrition was a lady as well but more along the lines of treating epilepsy–I don’t call her nutritionist though she may have been. 😉
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Terrific post……one of your best with thoughtful information and opinions that you will not read anywhere else……or at least I never have.
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Thanks Paul!
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I’ll drink to that 😛
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lol, enjoy
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