Is there a point to weight training during my fast since I’ll be consuming absolutely zero protein?
Or should I just stick with cardio?
Yes, it will help preserve muscle.
Specifically, since you have no protein intake, you want to avoid breaking down muscles too much. This means you should avoid higher rep ranges for hypertrophy and focus instead on lower rep range compound movements.
Take my advice with a grain of salt; I’m not a professional. Also my experience has been with 48 and 72 hour fasts, I can’t speak for longer fasts.
I personally don’t because I always tend to do too much. When glycogen stores are depleted high-intensity exercise can result in the catabolism of muscle as the body turns to breaking down protein for energy.
I’d say I’d you wanted to lift I would just do 1 set per body part and not to failure