Actually this is why I got into cycling. Last summer I noticed that all my T-shirts were starting to get tight, and I became self-conscious about how I looked. Pulled the bathroom scales out of the closet and was shocked to see that I weighed 280 on them, so pulled my old mountain bike out of the shed, cleaned it up, and started riding. Didn't lose much weight until I changed my diet. Now, happy to say, with a new bike and new diet, I'm 30 lbs lighter, my shirts all fit, but my pants don't seeing as how I've gone from coming close to needing size 44's to back to 38's.
All I can say is keep at the riding, watch what you eat, and you'll lose that gut and moobs.