I have to say, it is a little frustrating. I haven't gone through a mass gaining phase like this in a while. Already I am noticing my pants are tighter from the added fat on my midsection. I have never been good at accepting the fact that I will gain some fat along the way. I have to remind myself that I am also gaining muscle and I can worry about getting cut up later. I am definitely gaining muscle right now, but also fat.
Maybe I need to cut out the junk. I have gotten carried away lately eating a lot of peanut butter sandwiches, soy icecream, cold cereals, etc. It is fun watching my strength and size go up, but not so fun seeing the fat on my mids. Right now I am 215 lbs at a little under 6'3". One thing I am doing differently now is more of a power lifting program and only three days a weeek.
When I do a 4 day program, it is harder on my time, but I don't gain as much fat. Maybe I should add in some cardio. We are going to Disney World in two weeks and will be hitting the hotel pool, I hate to think I won't have definition in my and. LOL.
I have to at least get a little more lean by the time beach weather is here in June.

When you're in a surplus, you're going to gain fat no matter what because it's all about calories in/calories out and not the types of food you est. Adding in cardio will reduce your surplus and therefore your gains but it'll be both fat and muscle gains that will decrease since your calories will be going to fuel your additional sessions.