i train 3-5 days a week in the gym depending what routine i'm doing. I am fairly lean and muscular although i want to put on at least 5-10kg.
I am fairly active, train for soccer twice a week and play once a week. Combine that with gym and the occasional run, extra game of soccer, i burn a lot of calories. I'm not looking to get much bigger, just a bit biggger.
My question is how hard is it going to be to put on some weight?
I really struggle to put on weight and haven't really ever tried altering my diet significantly. Am i going to have to eat more calories to make up for how active i am? And this may seem like a stupid question so apologies but once i say put on 5-10kg, how hard is it to maintain?

Thanks in advance

Cheers

Carl