Without the proper building materials you can't build anything. Granted some people have genetics that allow them to eat things like a bowl fruit loops, soda, sandwiches and an occasional protein shake and grow like somebody who ate like a pro and trained their asses off.
It all has to do with metabolism, differing levels of hormones (test, GH, insulin, etc), and things like insulin sensitivity or amounts of androgen receptors. The list goes on and on but many things play a role in the ability to build muscle tissue and/or store fat.
Even if you have great genetics though, just think of how much faster you would grow if you took the necessary time and ate as well as you could.