Well if you're eating a guacamole bacon six dollar burger with a large fries and large mint chocolate chip shake after your rides, it's no wonder you're gaining weight. Keep in mind that on a 2-hour ride, you're only burning about 1000 calories. You can look it up by looking up the site of the fast food place you're thinking of, but the burger and shake will probably run you about 1300 calories.
If you have something about 250-500 calories to eat before the ride, and then eat a couple fig newtons (or something of a similar calorie count) mid-ride, you won't feel so hungry after the ride.