Originally Posted by
MinnMan
Interesting point, but I'm not sure where the cutoff would be and if it is the same for everybody, depending on their training. I've never been deliberately fat adapted and I used to be a total carboholic. However, when I am/was properly trained (i.e., had lots of miles in my legs), I have had no trouble doing centuries or up to 150 miles without fading at the end - that is, 5-8 hour rides. That's not ultra-endurance, but for me, the window is definitely greater than 3-4 hours. Without "fat adaptation". I do not favor rides longer than about 7 hours for other reasons.
Doing rides of that length in zone 2 automatically gets you burning a lot of fat. The benefits to timing of eating and exercise can have more benefits.
What I find interesting is looking at the training intensity and duration of professionals during the off season or "base" period.......early in the season. Lots of hours at fairly low intensity.
Specifically, exercise training after an extended, overnight-fast augments skeletal muscle adaptations such as GLUT4 and AMPK protein levels, and reductions in postprandial insulinaemia, even when energy balance is unaffected.
https://physoc.onlinelibrary.wiley.c....1113/JP280748