Bodybuilders are experts at loosing fat getting in to single digit body fat percentages consistently and methodically.
Most follow the same rough diet and manipulate calories in the same way, it’s kind of cookie cutter, do this you’ll loose fat.
Most of it is learnt over years of professional bodybuilders keeping meticulous diaries of every training session, every calorie eat, every small change made and every result seen.
Bodybuilders take it to the extreme to be the best, still I think if you are interested in loosing fat there’s a lot that can be learnt from bodybuilders without going to the extreme.