If you are even a little into fitness you will have heard about HIIT (High Intensity Interval Training) for fat loss. In simple words, this means doing very demanding movements for short intervals followed by a resting period. You may have heard that it is the best way to lose fat and preserve and gain muscle mass. But is it really the case? Let's analyze.
Before I go any further, let me just talk about the traditional fat loss method...YES...that's the one. Getting on the treadmill and jog for 30 - 45 minutes at a constant speed while keeping in your fat burning zone which is about 65 to 75% of your maximum heart rate. So if you are 30 years old,
you should stay in between 123.5 to 142.5 beats per minute (220 - 30 = 190 | 0.65 x 190 = 123.5 | 0.75 x 190 = 142.5). It takes about 60 - 80% of the energy from the fats. Anyone who hears this would be completely convinced that this is the best way to lose fat. But this is not really true. I agree that this will help you lose fat but I question the part about it being the best. Let's take a look at some of the drawbacks of this type of training.
First of all, if you ask me, it is extremely boring. Anyone would be bored doing the same thing without any variation for a long time, but maybe that's just me. If we look at the more scientific side, this kind of cardio training will raise you metabolism (or use of energy) during the workout and an hour after the workout, after that you will get back to the normal metabolic rate. So you don't burn a lot of calories at rest. Then there's this problem of hitting the weight loss plateau. This means that you stop losing fat because your body gets used to your workouts and diet. Another huge problem is that when you workout for over 35 - 40 minutes you increase the release of a hormone called cortisol, which is a regulator of all the human body functions, but one of its not-so-good features is that breaks down the protein for energy (i.e. muscle loss).
Let me also point out that muscle is heavier than fat so the scale will show that you have lost a few pounds but losing muscle mass is no good. The final and most important goes back to the first point where I mentioned that this cardio burns more fats and fewer carbohydrates. But if we look at our diet, we take a lot more carbs during our day compared to the amount of fats and if we don't use up those carbs, they eventually convert into fats. So whatever benefit you get, will not be the best result.
Now that we know quite a bit about the traditional cardio method, let's look into the HIIT method of cardio. As mentioned earlier, it involves short burst of highly intense movements followed by recovery periods. So as an example, a very popular HIIT workout is to jog for 2 minutes and sprinting for 10 seconds and repeating this from 5 - 10 times depending on your fitness level. Research shows that this kind of training elevates your metabolic rate for a number of hours (ranging up to 48 hours after a workout). This is due to the EPOC effect. EPOC stands for Excess Post-exercise Oxygen Consumption, which basically means that you use up more oxygen at rest after a workout session compared to the amount of oxygen used pre-workout.
EPOC is accompanied with a higher metabolism, which is exactly what you want to lose fat. I would like to make it clear that long traditional cardio also gives the EPOC effect but for a very short period of time. Research shows that anaerobic (weight lifting, sprinting etc) workouts keep you metabolism higher for a lot longer than traditional aerobic workout (jogging, walking, , cycling etc.). At the end of the day, you burn a lot more calories, which include both carbs and fats.
Another effect of HIIT form of training is the release of testosterone and growth hormone which help build muscle but at the same time, a number of research shows that they help lose body fat and preserve muscle. Because HIIT is done for no more than 20 minutes, the release of cortisol can be avoided. Other benefits can include that HIIT helps you give a better tone to the entire body, it is not boring as you keep changing and planning every minute or so. HIIT is often used to break a fat loss plateau so your body will never get used to a workout.