I can see why you are confused!
First of all, how can someone say they took in zero fat, that is impossible, even tuna has fat in it.
Then, the person that said zero carbs, but eats fruit; fruit is ONLY carbs.
The truth be told you need both.
20 to 30 percent protein, 40 to 50 percent carbs, and 20 to 25 per cent fats.
Ever see a body builder?
Google body building cutting cycle.