When i first started the 16 hour fasting it was a tough adjustment. Hunger arrives because I broke my usual eating patterns and headaches sets in. Eventually adjusted to the changes, did not feel like doing anything but had to just do the workout, through sheer will. I feel tired, but my health improved because of it. After working out, I feel a lot better, and I have felt noticebly stronger when doing some lifiting for everyday task.
I'd say do them but start small, adjust and increase it over time. During the fast my wil was brittle, felt like my body was eating itself, didnt want to think about anything. Perseverance and if you mess up, start again. Good luck and stay strong.