Well it sure would stop the fast I would however say watch the heck out for a crash from the fast acting carbs and protein if thats All you have post w/o. Have another serving ready to go or sip some during the w/o.
That said I love Surge prior to/during my w/o's and yes it raises intensity.
I am Not a big beleiver in fasted excersize aside form low-moderate cardio a brisk walk. any thing higher than that and your just asking for LBM loss and lower performance to boot.
Just my 2 cc