BfB is designed to gain muscle and strength not as a fat loss tool. It has to be done on a caloric surplus, not a deficit. You can use the same circuit/complex approach for fat loss but with higher reps and lower intensity. Something like:
2 circuits of 3 reps (with approx. 80%) then 2 circuits of 1 rep (with approx. 90%), then 2 circuits of 6 reps (with approx. 70%)
This is your training day.
I'd do it 3-4 times a week and once or twice I'd do sprint sessions or loaded carries.