No. Lightheadedness is a function of electrolytes.
Once ketones rev up, you can lift without issue.
I went 19 days and only stopped when I felt that my metabolism had dropped too far. That’s why I’m modifying my current 3 day “fasts” with protein.
I hit 9.3 ketones in the last week and had lots of energy to burn.
The difference is intensity. Without replenishing glycogen, muscles can’t do heavy excursions… so I could do high rep, high volume, low weights forever… but heavy weights to failure were hard.
Also, legs were hardest. It’s a large muscle that consumes massive energy and it feels much harder when fasting.
So I would do cardio or something else on those days … and that’s where I lost the most lean mass. Check out my fasting thread for the details.
Fasting is a mental challenge. The body is amazingly strong, but the mind is weak without training. Thankfully fasting strengthens the mind.
I know they say the spirit is willing but the flesh is weak. That’s only true on SAD … when I fast, the spirit is strong and the body is strong… but the mind starts off weak and gets stronger.