i'm a pretty thin guy. 6'1 and 155 pounds. i went to the gym a fair bit during the summer, got stronger, i'm as strong as guys who look much more muscular. what can I do to gain a bit more muscle mass? people at my work told me that i have to put on a lot a fat and then turn that into muscle, that's doesn't really sound like a great idea to me...but i don't know much when it comes to fitness or anything. so any particlar exercising/diets that people could reccomend? or anything else... I'm 19 years old btw. thanks!