Burning 2000 calories on a bike ride seems like a stretch unless your riding for 8-10 hours.
According to the Cleveland Clinic Center for Consumer Health, a runner who weighs 130 lb. will burn 2,224 calories during a marathon, a 165 lb. runner will burn 2,822 calories and a 210 lb. runner will burn 3,593 calories
Read more:
http://www.livestrong.com/article/30...#ixzz2Z24wiepg
You may be using incorrect information, skewing your calculations. Calories burned on a 40-60 mile bike ride is in the hundreds, not thousands.
p.s. You and I and everyone else knows that the only way to gain weight is to eat too much. Sometimes we just don't really realize how much we eat and if your like me, we really don't count everything.