oh, I read that wrong, I thought you asked about 6 months, not 3 months. Well if anyway, if you have enough muscle mass and low enough body fat, then 3 months should probably be enough. 20% BMI... wonder what your %body fat is, I don't know but I would guess that when a man is ripped he is probably not more than 10-12% body fat.
By the way would you mind sharing what your goal/motivation is? Just curious.