I can't figure out why your main concern is football. Anthopometrically, you are well suited to play DB and be a sprinter. If you gain 40lbs, I can tell you with absolute certainty that you will be much slower. I'm assuming you are a HS football player, you'd be better off if making the position change and staying at more comfortable weight say 180-185lbs. Even at the highest levels of HS football LBs can weigh as little as 150lbs on some very good teams. No college coach worth their weight in coaching is worried about mass over intangibles such as speed and strength, they have Strength and Conditioning coaches at the college level along with dieticians and training tables that help athletes put on size without having lose much of their athletic ability. It's even not unusual for OLBs in college to weigh 190lbs as freshmen. One thing is for certain, putting on so much weight so quickly will ruin what athletic ability you do have right now. The biggest concern for HS athletes should be how do I stay in shape, and keep that shape while building on sport specific capabilities year round not gaining mass then work sport specific abilities.
