More total calories burned. Although high-intensity aerobics will burn a little less fat than its moderate-intensity counterpart during the exercise session, the total number of calories (and fat) burned as a result of the former is substantially greater than that associated with the latter. This is due to an increased excess post-exercise oxygen consumption (EPOC). In other words, the number of calories burned during the hours following a high-intensity exercise bout is greatly increased due to a prolonged increase in oxygen consumption. With low to moderate intensity cardio, EPOC is minimal, thus metabolism quickly returns to baseline following the exercise session [6,7].
Greater fat loss. In one particular study, individuals performed either an endurance training (ET) or HIIT training program for a period of 15-weeks. At the end of the testing period, the HIIT group experienced nine times the fat loss of the endurance training group . This is certainly supported empirically by the many individuals who have experienced accelerated fat loss after adopting HIIT as their form of cardiovascular exercise.
Greater increases in maximal oxygen intake and overall level of fitness. High-intensity interval training has proven to increase both one’s aerobic and anaerobic capacity; endurance training only increases the former [1,2,3,4]. Moreover, HIIT has been shown to increase one’s aerobic capacity even more so than endurance training . One study showed a 14% increase in maximal oxygen uptake and a 28% increase in anaerobic capacity in only 14 weeks when following a high-intensity workout regimen .
Here is an excerpt from a recent article I composed:
I recommend conducting all cardiovascular activity in the morning to take advantage of the prolonged increase in metabolism. It is OK to have a small meal before your session as doing so improves performance and has a negligible impact on energy substrate utilization both during and after exercise [9,10,11,12]. As far as post workout nutrition is concerned, it is fine to go ahead and supplement with fast digesting proteins and carbohydrates immediately following your HIIT session. While the theory of waiting an hour before consuming a post workout meal/beverage sounded solid, it didn’t hold up when research put it to the test. Conversely, research shows that consuming quickly digested nutrients immediately following high intensity cardiovascular exercise actually increases EPOC, reduces muscle protein catabolism, and increases recovery, all while having no adverse effect on lipolysis (fat burning) .
This is a highly complicated question. A single meal isn’t going to yield much (if any) physiological benefit; it will only yield a psychological benefit. To get the physiological benefits (what you really need), the duration of the overfeed/refeed/cheat must be longer. The key is too keep carbs high and fat low to minimize the damage.