Intensity is measured as a percentage of your maximum heart rate (HRmax), which means the maximum safe heart rate. Maximum heart rate varies with age, but basically this is calculated as 220 minus age for adult (maximum heart rate measured in beats per minute). The intensity of the exercises can be divided into low (up to 70% HRmax), the mean (70-80% HRmax) or high (80-80% HRmax).
Low-intensity exercises improve efficiency and you can do them over a long period of time. Because for a long time is consumed a relatively small amount of energy metabolism has time to process the fat for energy. It is estimated that approximately 50% of the required energy comes from fat and 50% from carbohydrates. This means that this is the recommended type of exercise, if we set for ourselves the goal of capturing the weight. At a higher intensity exercise most of the energy is taken from the carbohydrates.