Why not do an upper body workout as well? Lose fat and gain muscle. It puts the fat storage to good use as it uses it for energy when you lift weights as well as running.
It's difficult with me because I have a low body fat percentage meaning that i'm quite lean. I have to shove food down my throat to give my body the energy to work and also leave some reserved for weight gain. Then I have to lose it again.
try different things and do what works best for you. For example I train for strength and practical muscles, not to build visual muscles, so my training looks very different from the majority who is just there to change their appearance. A massive advantage of training different body parts is that you can go to gym 7 days/week and come in to more of a rhythm. In either case it is important that you give the muscles enough time to build up again afterwards. and that you eat right.
Also, I get the impression you are fairly young? Pumping iron is likely to lead to a stop in your growth. I have a friend that this happened to.. he is muscular, but very short, and quite annoyed about it.
^what 2Z said is 100% correct. Biologically speaking, any male under the age of about 19 (depending on when your growth stops) should only really life about 5 pounds per arm. Any more and your growth will stop before it is supposed to. I saw this at my (now former) school, with most of the shortest guys also being those that worked out the most when they were between 14 and 17.
Don't try to bulk up (too much) until your about the maximum hight that you will be.
Guys, guys, i'm 16 but i've reached my max height already. I'm 5'9 which is just above average height and i'm quite happy with it because that's extremely tall for an asain person.
Currently i'm working on appearance and strength because i'm quite thin but muscular as i've said and i have high metabolism. Currently lifting 16 kg dumbbells for chest presses and flys.