While you burn more calories when cycling at a higher intensity than a lower intensity for the same duration when it comes to intensity, "more" is not better for weight loss. This is because fat oxidation to energy needs falls off very quickly above about 80 percent and become very minimal at about 90 percent of your max heart rate. This means that at greater intensities, you are burning muscle glycogen not fat. The ideal fat burning zone is 60-80 percent of your max HR according to a recent study by Achten et al. Another thing to remember is that if you eat a high G.I. carbohydrate prior to or during your Ride you may impair the fat oxidation process reducing the amount fat you will burn during that exercise. So for rides shorter than about two hours, skip the pre-ride energy bar, stick with water (or a electrolyte without a carbohydrate) in your bottle, and keep your intensity in the ideal fat-burning zone of 60-80 percent of your max HR. A low intensity program done in the fat burning zone is also ideal for those who cannot tolerate high intensity exercise. Therefore, those beginning a program, overweight people or individuals restricted due to medical problems will benefit from a low intensity program. But, if you are a seasoned cyclists able to Work at a higher intensity do so, because you will burn more calories.