I've been fighting the weight thing all my life, and in fact got into cycling initially to lose weight. Basically, it takes a lot of time and persistence to shed pounds and keep them off. Unless you are competing, it's far more effective to ride daily at a zone 3 aerobic level of effort to get good cardio and maintain low body fat, and use light weights to maintain upper body muscle tone and mass. Also, it's very important to work on core strength with various calisthenics.