Riding for transportation doesn't burn as many calories as riding for exercise.

Still, your weight gain is probably from muscle mass. Remember that muscle weighs more than fat. I used a few online calculators and found I should be eating around 2700 calories a day to maintain my weight. I tracked how many calories I was eating for a few days, and that was about right.

The best approach to eating should be only eating when you're hungry, and eating unprocessed foods (stay away from TV dinners, hamburger helper, etc.).