I've been doing low carb on and off for a few years now, and have actually found it fine for athletics. The most striking example is that I ran a tough mudder (

I've been doing low carb on and off for a few years now, and have actually found it fine for athletics. The most striking example is that I ran a tough mudder (20km run through mountainous obstacle course; takes 4-5 hours) on nothing but a big portion of bacon I'd eaten that morning. I still felt full of energy at the end. I'd brought a bunch of snacks with me to be safe, but never ended up needing them. By comparison, I've done some other endurance stuff while not on low carb and there's no way I could have gone that long without refueling.