I do low carb, not true Keto, stay under 100g of carbs daily. With that being said, I did <30 net grams daily and tried to ride. Did a 20 mile ride and bonked hard enough to rethink what I was doing. On <100 net grams a day I have plenty to go on that 20 mile ride and for longer rides we pack some GU. I find that we need to have one after every 25ish miles. YMMV

I say try it, you can definitely lose weight on a Keto diet. Be prepared, have some GU or something to get you past a bonk, as you more than likely will have one on a longer effort.