Well, look at the top level cyclists. Most of those guys do not have any upper bodies. There is a reason for that. You don't use your upper body much in cycling and every pound is weight that you will need to lug up a mountain pass while trying to beat a guy who looks like an anorexic mountain goat.
So if you get rid out your excess weight and ride hard, your upper body will decline.
Now the vast majority of cyclists are not going to try or need to climb with a elite climber. So, if you want tone and some mass in your upper body, you can use some moderate weight lifting to keep that side up. Having some upper body may hurt your climbing some but it is nice to be able to lift a full milk jug.