That's extremely unhealthy, Just like you lose weight GRADUALLY you should also gain it slowly. Eating tons of junk food will make you sick, and most likely give you nasty stretch marks, because that's what happens when you gain weigh too fast. Focus on trying to gain muscle & not just fat !
I'm not eating junk foods, so how do I gain muscle?? pls give some advice, tnx
read this: http://funadvice.com/r/3k0qm094ng