Don't listen to some of these replies. I lift 5 days a week and bike about 4 days for 30 miles or so. The key to building muscle if that is what your after is eating a caloric surplus while ingesting 1 gram of protein/ lb of body mass. So if you weigh 170 lbs you need to eat at least 170g of protein/day if you want to gain muscle. The same is true if you just want to lose body fat. By adding cycling into your routine you just need to compensate by eating additional calories that you burned from cycling. This is a fantastic site I use to calculate your macros (fat, carb and protein)

http://www.1percentedge.com/ifcalc/

at the end of the day it is all calories in vs. calories out. As long as your above your daily requirement including the calculations for the additional cycling cardio you will gain weight, and as long as your diet is decent and you lift heavy in the gym you will gain lean body mass with minimal to no fat gain.