are you saying you ride for only 20 minutes? How much do you weigh? How fast do you go? The problem may be you're not exercising enough. 3-6 miles walks are good exerecise but they aren't going to make you lose a noticeable amount of weight. Also, not eating is not good for weight loss. Your body slows down it's own metabolism when you don't eat, meaning you start to burn less calories. Always eat at least 3 meals a day. They can be small but always eat three times a day.