If you've seen the movie "Supersize Me," then you'll know why it's not good to eat fast food. Wangho says he could be fabricating his story, although there's a guy in the movie who eats Big Macs all the time, doesn't exercise, and manages to stay thin. Well, he may be thin, but he's not healthy. Fast food has hardly any nutritional value, so you're depriving your body of important nutrients that are necessary for muscle growth.
Wangho, if you want to bulk up, you need to eat a lot of food to go with your weight lifting routine, but it needs to be quality food. You mentioned that you eat things like tuna and chicken, and that's what you need more of, along with grilled salmon, fresh veggies, slow-burning carbs like whole oats and brown rice, and some of the good fats, like those found in almonds, avocadoes, and flaxseed. Supplement with whey protein shakes, especially after working out, and if you're taking in enough calories, you'll start to notice a change in your physique pretty quickly.