I recently started the Keto diet and it has been going well in terms of weight loss. I ran into a snag yesterday. After 11 days on the Keto diet, I decided to go for a 19 mile bike ride. I had done a 10 mile cruiser bike ride earlier in the week with no ill effects, but yesterday I went on a 19 mile ride on my cruiser bike again. The ride took me about an hour and 45 minutes to do. The wind was really high (20+ mph) and I came to find that my back brake was rubbing when I got home, those things usually add a little fatigue to my post ride, but nothing like I experienced yesterday.

Before the ride, I ate a big, zero carb breakfast. During the ride, I felt fine. Immediately after the ride, I felt fine as well. I didn't eat for two hours after the ride and started to feel bonky. So I went and ate a bigger meal that I had in several days. Not really high carbs, but not super low carb either. Continued to feel hangry after the meal and lethargic. Went grocery shopping and had to drag myself through essentially. Got home with little energy and actually took a nap, which I never do.

Ate a small near zero carb dinner and went to bed. Slept 9 hours which is long for me and woke up this morning still feeling slightly fatigued. This coming from a guy that has ridden 4200 miles this year and recently did a 3-day, 160 mile loaded bike tour like it was nothing before starting the Keto diet.

I'm asking this question to a specific group of people just in case anyone here might fall into this category. Are there any longer mileage cyclists on the keto diet on this forum? If so, how did you go from being a sugar-burning cyclist to a fat-burning endurance athlete and keep your energy up?

Do you still carb up before rides? Or do you ride in ketosis? What method have you found that let's you ride the same way you rode before going keto?