They have no idea just how incredibly hard it is to add muscle mass.  That's why bulk and cut cycles are popular; it's easy to lose fat, but very very hard to gain muscle so you don't mind adding a non-trivial amount of fat if it means maximizing muscle gains. If you're new, lift very hard, eat very well and are male, you could do 20 pounds in a year.  That drops off pretty fast once you are past noob gains.    The women's physique winner in the 2014 Ms. Olympia contest was Juliana Malacarne, who has an off-season weight of 130 and is 5'2".  That still comes out to only a BMI of 24.  So no, fatty, your BMI is not 50 because you are strong.