Yeah, but what do you know? 
Just kidding, great to see you here Dr. 
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You can live without glycogen stores just fine, longest fast I ever did was 4 days and I could continue doing moderate exercise just fine but the longest fast ever was over a year long without any detrimental effect. Your body is quite capable of making glucose from other substrates and in fact only 1 cell type is completely dependent on glucose (red blood cells) the rest can thrive with other fuels
Can you be more specific here? Youâre not saying someone was able to survive for a year with no food are you?
yes someone survived for 382 days without any food
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I wonder what his first meal was after that.
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I think this is still a million dollar question actuallyâŚ
I think that to a certain degree the absorption is a limitation despite the ability to tolerate big amounts of carbohydrates. Where this absorption limitation lies I have no idea and I donât want to speculate too much. The next question is what happens to the carbs that end up being absorbed.
At rest, they get stored. During exercise, they get oxidised. But they will only get oxidised based on the demand. If the demand for them isnât sufficient, they wonât get oxidised.
Also, keep in mind that insulin levels can get increased even during exercise and this then âunlocksâ other cells to start taking up glucose and this can lead in storage of carbs in the inactive tissue for instance. Like arms. So you will never see 100% efficiency in oxidation of those ingested carbohydrates. But the higher the demand for carbohydrates, the higher the efficiency of their oxidation.
We have some cool data on the topic to show but we first need to get them through a peer review in a journalâŚ
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something small and with lots of certain electrolytes (potassium, magnesium and phosphate )
To circle back to the fructose specific concerns (as I understand them) is that fructose metabolism results in increases in blood serum uric acid levels, which then causes (or at least highly correlates) with various bad health outcomes. Here is a paper (one of many) by Dr. Richard Johnson describing this: https://academic.oup.com/edrv/article/30/1/96/2355050
From my very brief search for papers on this not by Dr. Johnson (him doing the podcast circuit and selling books on the dangers of fructose puts me off a bit) it seems like many of these studies involve overfeeding of fructose - ie a calorie surplus including significant amounts of fructose is maintained for many days. It was not clear to me if these same effects were observed if there was no overfeeding, and calorie balance was maintained. So while excessive fructose as part of a calorie surplus diet seems to have issues, I really wonder how this applies to fructose consumption during exercise.
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It doesnât. Iâve done a fructose overfeeding study myself and this looks horrible. You basically give out fructose in bags and you ask people to eat fructose. It doesnât really happen like this in the real worldâŚ
Also - did anyone ever see a healthy outcome from an overfeeding study? Overfeeding with fat is bad. Overfeeding with a healthy diet is also bad. So?
Keep in mind that the problems will occur when the liver will be saturated with glycogen and the demand for glucose is low. There is a nice study by Luc Tappy showing that if you remain active, negative effects of fructose in large quantities disappearâŚ
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I know the bacon cheeseburger and fries I had after 2 day fast for a colonoscopy a couple years ago didnât sit well! 
Sure you can do without eating any carbs. What we are talking about is being able to perform at high intensity for long periods of time. Thatâs when carb consumption is needed.
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This appears to be the referenced paper: " Health outcomes of a high fructose intake: the importance of physical activity" Apparently as part of a 3 day fructose symposium.
https://physoc.onlinelibrary.wiley.com/doi/full/10.1113/JP278246
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This is a great discussion, especially the appreciation for knowledge gaps. Thanks everyone!!!
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I mean he lost 276 pounds, died at age 50 and put his fatherâs fish and chips shop out of business⌠I donât know that we can say no detrimental effects
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We donât know the cause of his death, his lifestyle post fasting nor how old he would have gotten without the fast
You canât outbrush frequently repeated challenges with sugar. If you drink sugar all through the day for many days of the week you are almost surely going to end up with many cavities. For your teeth itâs much worse to frequently consume small amounts than a big amount in 1 go
Thank you everyone for engaging with this post. Was especially excited when I googled who @timpodlogar was!
To sum up, it appears that:
- Consumption of sugars/sugar water is fine during cycling as long as it is not a recovery ride. This is because the utilisation of sugars is higher than what we can supply e.g. ~100g/hour. The carbs are oxidised during exercise (instead of stored) and insulin remains low (especially if higher intensity).
- There is no particular concerns with fructose as long as its during exercise and general energy balance is maintained.
- It is worthwhile to check in with a doctor or get blood values to ensure values are in a healthy range. âhb1acâ should be monitored.
- Sugar water is not great for dental health. To mitigate, brush teeth before, sip more less frequently (if possible) and chase with water in a spare bottle.
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Exactly. We know he did it and survived, but we donât know about the long term effects one way or another - except that he put his dadâs shop out of business
sorry for being dense, but what is the difference that causes the two different outcomes with these images? Is it exercise?
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