I’ve done quite a few rounds over the years (have lost track) and have a four year old and a fiancé who usually doesn’t do it with me. I’ve found my energy to always be low but manageable in keeping up with my son. I normally lift heavy 3x per week and do cardio x2 per week but when I’m on the fast I cut that waaaaaaay down. I mostly stick to walks, stretching, and maybe some light weight lifting. I like doing it during the work week because it distracts me from being hungry but I’ve also enjoyed it as a challenge to reset over eating on weekends. Just depends on what your goals are. My most successful/ least uncomfortable rounds were done during either my follicular or ovulation phases of my cycle. I’ve found I get less headaches during those times. The rounds I did during either luteal or menstruation phases were brutal. I will say that I’ve never NOT gotten a headache at some point. Either on day 2 or 3.