Hey All, This discussion reminded me of one of my favorite writing about this topic, from the guy who fed Tour de France teams as a career for 10+ years: Allen Lim (who went on to found Skratch Labs)
You can read the Intro to one of his books here (amazon free preview of the first 70 pages) It goes into depth of why, Chris, you could do that effort fasted, but why on harder efforts, you would bonk. There’s enough glycogen stored in your body to put up with that amount of effort for a while, and fat burning (even if you are ‘fat adapted’) is so slow it barely makes a dent in the calorie deficit you develop at high intensities. As an aside, Lim writes, working at about zone 2 you can use about 50% from fat vs glycogen, but that ratio drops the higher intensity you go.
Lionel could’ve taken this advice:
Again, in the writing he talks about sugar being used as a tool. If you try and replace all the calories a TdF rider uses in a day with solid food, he’d be on the toilet all the next day instead of the saddle.
Some good charts from the intro of the book:
