I had a similar experience when trying a keto diet - I struggled to cycle up a single short hill on my commute home, despite being a moderately-fit regular cycl

I had a similar experience when trying a keto diet - I struggled to cycle up a single short hill on my commute home, despite being a moderately-fit regular cyclist. Bringing the carbs back in solved this. YMMV. It's interesting that even some of the more pro-keto/paleo/primal blogs often recommend carbs (albeit appropriate quantities) to support any significant level of exercise.