Ofcourse you can.
I was a skinny little japanese when i started. Many years i had thought that i didnt have genetic.
But now i have same mass as NPC light heavy competitors when i realized that YOU CAN GAIN MASS SAME AS PROS WITHOUT DRUGS.
Also my friend freaky Ogawa is living proof. His weight is 135kg natural BBer.
Ogawa has been my friend since i was 20years old. Now i am 37years old.
I know him very very well.