I’m doing Keto since the beginning of this year. Mainly because i have fatty liver disease.
Once a week i’m doing a very long and intense bike ride (5 hours). On this bike ride I eat sugar and carbohydrates.
Does this sugar gets processed by the liver or is it instantly used as i’m intensly exercising?
Does this sugar still have a bad impact on my liver? or is there less impact when I instantly ‘use’ this sugar?
Table sugar (sucrose) is a disaccharide consisting of a glucose molecule bonded to a fructose molecule. The bond is cleaved, and the glucose is dealt with in the normal way, while the fructose is sent to the liver to be dealt with. The metabolic pathway that handles fructose also handles alcohol (ethanol) and branched-chain amino acids (BCAA’s). The problem is that this pathway gets easily overwhelmed, and that is what causes fatty liver disease. The more sucrose you consume, the more your liver will have a problem with it. So you’d be better off with a glucose gel than with sucrose.
Fatty liver disease is easily reversible. One pilot study showed it happening in about ten days. The key is to avoid sucrose/fructose and strictly limit ethanol.
That’s interesting. Wasn’t it Dr Phinney who was a keen cyclist and wanted to show how ‘low carb’ didn’t work well for exercise … Only to reverse his opinion?
Yep. He said that on keto, he can cycle for miles and miles and has become virtually bonk-proof. He also has a great story about the winner of the Western States Iron Man 100 a few years ago now, who went out and ran a marathon the next day, just for fun. (His time was really good, too, as I recall.)
Here is a fascinating lecture I just watched, and which is broadly relevant to the topic:
Thank you very much for your answer! This is very interesting!
What do you mean by “the glucose is dealt with in the normal way”?
Is glucose not bad for the liver? So i can still eat glucose and dextrose with fatty liver disease?
Normal sugars get processed with everything else, Fructose by the liver. Eating keto and having nearly no stored glycogen combined with a ride like that means it really makes near zero difference what you do, you’ll be incinerating it all as fuel long before you store any of it. Enjoy the fast energy.
Glucose isn’t bad for anything, without it you’re dead! Same goes for fructose. It’s excessive amounts that are a problem, but even that’s dialed back when it comes to endurance training.
Glucose is not dealt with in the liver at all, except to make glycogen (the storage form) to be shared with the muscles at need. (When the muscles make their own glycogen it has to be used by the cell that created it; it can’t be shared, for some reason.) The paediatric endocrinologist, Rober Lustig, says that liver glycogen may enlarge the liver, but it has absolutely no harmful effect. (And the liver apparently shrinks again, as that glycogen gets used up.)
So yes, you can still eat glucose and dextrose with fatty liver disease. In fact, Dr. Lustig and his team showed just that, by taking a small population of obese children (this was a pilot study) and switching their diet from one with a high fructose content to one with almost no fructose. To keep calories constant, they replaced the fructose with glucose (as he puts it, “Instead of fruit, we gave them bagels.”).
Now, too much glucose causes other known problems, such as hyperinsulinaemia and the whole cluster of diseases known as metabolic dysfunction. But fatty liver is not one of those problems.
So you’ve been doing this for 6+ months? What happens if you don’t eat anything during your ride?
What is intense? The average person has about 60,000–100,000 calories or fat in their system. Fat can be used as your main fuel source at lower intensities if you are fat-adapted. Those with diabetes and pre-diabetes have a hard time burning fat. Even at low intensities, their blood lactate level is above 2 mmol/L. The body prioritizes sugar as fuel when it is above 2. Do you know your FTP?
Generally, for simplicity’s sake, the sugar goes directly back to the muscles. How many carbs are you consuming per hour? World-class cyclists can consume 100+ grams of carbs per hour. Keep in mind that they are the best in the world.
I recently did an intense century (averaged 32km) and consumed about 45 grams per hour with no issues. 20 grams from my hydration drink mix and the rest from energy bars (carbs: 23 grams, protein: 12 grams, and fat: 8 grams).
You may find that this is not enough or too much. However, I do find it works for me, and especially the next day, I can still go out and do a 2-hour fasted coffee ride with no issues.
If I don’t eat anythin, I feel I lose power. I can continue to ride, even 150km with no carbs/sugars. But at a much lower speed…
