My experience with keto was that my ability to exercise intensely plummeted.
I could only do relatively low intensity cardio - no sprints, and I fell far from maintaining my previous threshold pace.
I did lose weight effectively, and seemed leaner.
Exercising while in Ketosis is one of my interests. Here's a thread I started yesterday:
I exercise daily, on the treadmill, at a heart rate of 115 to 120 BPM. At my age, this is well into cardio. So far, I have had no adverse reactions.
For my personal knowledge base, please define "exercise intensely". Also, what adverse reactions did you have?
Thanks.