Will exercising make my bum bigger or smaller ?

If you do the elliptical bike on a high resistance you will get more muscle on your butt, which makes it bigger. The more cardio you do the more fat you will burn. When I ran varsity cross country, my butt was smaller because of all of the cardio I did. Now that I reduced my mileage of running, I got more of my curves back which i enjoy. If you want to gain more on your butt do weights with a higher resistance but less repeats. If you want it smaller or just toned, do lots of repeats without weights or less heavy weights.