If you are recovering between workouts and feeling adequate energy during these base aerobic runs then you are fine doing this. Top athletes I work with almost all their Z1-2 runs in a fasted state. If the runs get over 2-3 hours then you may need to carry and emergency snack of some sort. But, even those longer run will get easier to do in a fasted state as you adapt. To speed recover I suggest eating right after you finish. I notice that if I miss this feeding window after a long fasted run, I’ll feel that workout fatigue for as much as 48 hours where as if I eat immediately after I finish I’ll bounce back in a day.

Scott