In most cases more fat is burned after exercise due to hormonal changes, damage repair, increased metabolism, etc. than is burned during exercise. For many people higher intensity exercise (like HIIT or vigorous resistance training) will result in more total fat burn than long steady low intensity exercise. However the intensity level for HIIT should be such that after 20 minutes or so, you simply can not do any more, or you are not truely performing High Intensity Interval Training, you ar eonkly doing interval training. The problem with long steady low intensity exercise is it tends to increase the hormone cortisol in many people, which signals the body to strore fat (under the assumption you will do another similar exercise session again in the future and your body will need a store of energy to support it). Of course, everybody is different and everybody's body reacts differently to exercise and a lot of it is psychological. The best exercise program for you is the one you will do over the long term. And also remember diet is also very important to body fat loss for most individuals.
