I doubt a BB could ever do so much and excessive cardio so he would loose muscleweight.
A body is a machine adapting to the tasks it´s forced to.
Too much food in your stomach,no blood for the stomach,but for the task->food goes into the toilet sooner or later->calories are gone,although they were in.
Too little rest/calories for recovery,muscles won´t grow and the latter.
So here is in my opinion the best space for intervention.
The body composition inbetween a certain limit,which is declared "normal" by BWI or any other model for population,is highly responsive to exercise but the amount of muscles (LBM) over this middel is not.
It´s determined by the level of hormones you are able to produce(maybe in response to exercise and food-intake) or admister.
The food isn´t that important although it gives an edge to the specific need of the metabolism during exercise,after excercise,at rest...
But it´s neartly neglible for a normal man,not competin at top-levels.
I know it,´cause I ate tons of fat and carbs at work and had a bf below 10%,and a resting pulse of 42 and lower and several sh*ts of the weigth of an elefant during the day.-sorry for this metaphor.
But let me point out ,we´re both right and the border between food and medicine may vanish,but in general `eating´ is the least hindering factor in achiving a bodycomposition(not/ or partially weight) you´re seeking for.
It´s just hard work,in my opinion.
FF