This feature calculates an estimate of calories expended from fat during a workout and it is expressed as a percentage of the total calories burned. This estimation is important in weight management. During exercise, energy comes from two sources, carbohydrates and fat. When you want to lose weight, you want to maximize the amount of energy coming from fat rather than carbohydrates. If, on the other hand, your goal is to improve your aerobic capacity or performance results by more intense exercise, carbohydrates are used as primary energy source. The fat burning percentage varies according to the intensity of your exercise. The principle is that at high exercise intensities the percentage of fat consumption of the total energy expenditure is less than at lower intensities. So for example, a low-intensity 40-minute brisk walk will burn more fat calories than a 30-minute jog at a higher exercise intensity. In general, fat burning percentage supports low intensity exercising.