For anyone not familiar with HIIT, it stands for High Intensity Interval Training. Basically a workout that a person would establish a either a few different exercises or an exercise that allows for short intervals of high intense effort, like a rowing machine, bike, treadmill, etc. But is this more effective than getting on that elliptical trainer or treadmill, getting the heart rate up and keeping it there for 30 minutes or so? What do you think?
Well, best thing we can do is break it down: I would imagine that most people reading this like myself, are interested in losing some fat, especially around the mid section. We know that we must burn 3500 calories in order to lose a pound of fat. So to lose a pound of fat a week, we must burn 500 calories a day more than we consume over a 7 day period. So if we keep our eating the same, that 500 calories would result in the following activities of long cardio:
The benefits of the long cardio is that almost 60% of the calories burned during the session are the result of fat. Not bad, however, we have to look at the downside of this too. Once we complete a bout of long cardio, within the hour, more like minutes, our heart rate has returned back to its resting rate, our muscles have minimal damage, so little is required in regards to repairing of muscle tissue. The heart was not stressed enough to increase it’s overall capacity and strength. We did open the arterial walls and allow more blood flow, which is a good thing in heart health. But lets take a look at HIIT.
Completing 20-30 minutes of HIIT unfortunately is not track able in regards to caloric expenditure unless you are completing on an apparatus that tracks the overall calories, but what we do know, is that this form of exercise typically takes the heart rate into maximum values, forcing the heart to respond and become stronger over time. This type of exercise also pushes the muscles beyond normal exertion forcing muscle damage requiring muscle repair over a 24-48 hour period. So what does this mean? When we push the body beyond normal capacity, once the bout of activity is completed, our body must repair itself. In order to repair, it is going to require more energy expenditure for those 24-48 hours, simply put, our metabolism is now at a higher level causing our base metabolic rate to be a higher state, burning more calories while we are at rest. Not too mention, that repair is now going to increase the total volume of the muscle fiber itself, requiring more calories in the day to keep its current volume. Basically, the more muscle in volume (size), the more calories our body requires to maintain that muscle volume.
In a study produced by the Journal of Obesity by Stephen Boutcher, it was cited:
“Possible mechanisms underlying the HIIE-induced fat loss effect include increased exercise and postexercise fat oxidation and decreased postexercise appetite. As mentioned, Gaitanos et al.  have suggested that towards the end of an HIIE session that consists of numerous repeat sprints (e.g., ten 6-second bouts of maximal sprinting) an inhibition of anaerobic glycogenolysis occurs and ATP resynthesis is mainly derived from PCr degradation and intramuscular triacylglycerol stores. That increased venous glycerol accompanied HIIE in both trained female cyclists and untrained women  supports the notion that acute HIIE progressively results in greater fatty acid transport. Also Burgomaster et al.  and Talanian et al.  have shown that 6 to 7 sessions of HIIE had marked increases in whole body and skeletal muscle capacity for fatty acid oxidation. (here is the link to the study)
Basically the study is stating that fat loss from HIIT occurs far after the bout of exercise is completed, in addition to the body requiring calories to return to normal levels of muscular glycogen (energy stored in the muscle) and muscle repair. When our heart rate levels are low, as in the repair phase after the exercise, fat is a dense energy fuel that can be broken down with sufficient levels of oxygen.
To summarize, yes, if you want to take a walk in evening with your family it will be a good way to not only burn a few calories, but probably some mental clarity will be good for you too. But let’s face it, if you are like me and are past the age of 35, you have probably seen a dramatic drop in your testosterone levels and regardless of how much you try to watch what you eat, you are gaining fat around the mid section faster than you ever thought possible. The best way to attack this, is through some HIIT which can be done with some simple or even no equipment! high-intensity-interval-training This is a good starter guide.
Good luck with your bouts of exercise, if you have never done any HIIT, start small, and look to incorporate more of it into your workouts!
Live happy and healthy!