I do cross country / mountain biking, and I sometimes ride fasted on the weekends. I do not enjoy it. My riding is slower and I need more breaks, which is demoralizing, especially when guys older and heavier than me pass me on the trail asking condescendingly “are you OK?”
If you decide to do it, take electrolyte pills with you. The pain of most body muscles cramping when you run out of electrolytes and you are on the far end of the trail is not something you want to experience.
I have done a plenty of fasted rides.I have a roadbike and usually go for a flat ride. After about 40km i will get bonked really hard so i plan it in that way.In my opinion its pretty great way to get into ketosis, so i started my fast with this.
When i tried to go longer, i didnt have enough energy, but thats mostly because i wasn’t keto adapted properly. Without that, i am ot sure if its possible or it wont be enjoyable. But you do you, try it out with a few backup gel in your backpack.
Anecdotally, a 20 mile, 1500 foot elevation ride yesterday ~70 hours into a fast left me winded and bonking hard. 3 mph below average for the route, but I finished. It’s doable, but expect a significant drop in performance.
Extremely doable if you work your way up to it. Used to do up to 3 hours of fasted cycling at moderate intensity. Like 40-50mikes with just water and a 10 calorie BCAA supplement drink. Started with a double espresso and lots of water and could go for about three hours before really feeling it. Wouldn’t break my fast for another couple of hours after I got home.
I ride fasted all the time.
On Weekends I leave the house with just coffee and down a few glasses of water. I can do 20miles ish on my MTB before i feel weak. And that’s about as much time as I can spend riding on weekends before heading back home for honeydoos.
Note: I think I am able to do this because I used to fast on weekdays and then do relatively hard workouts after work before eating anything. Now that was tough! Not eating all day and then doing 2x 20 minute level 10 sessions on the escalator machine at the gym. I was pretty starving by the time we made dinner, but even this i adapted to pretty easily.
I’m good on slow endurance rides up to about 30 miles. Beyond that, I need carbs. I discovered this at mile 40 last summer. I ended up raiding a 7-11 for all their carbs after I bonked. No fun - but your mileage may vary.