When you exercise you burn both fat and carbohydrate. However, the proportion of fat and carbohydrate you burn varies and this is all dependent upon the intensity of the exercise of which you are doing. Now, burning fat is something I’m particularly interested in and I’m sure a lot of you are too and I would love to know what intensity of exercise I should be doing in order to get rid of that pouch of fat around my stomach that just does not seem to want to budge!
So, having done a bit of research I found that at very low intensity exercise, for example walking, you are mainly burning fat whereas at high-intensity exercise such as sprinting, you tend to dip into the carbohydrates stores for your source of energy. So why not just walk everywhere to burn fat? It’s a hell of a lot easier than sprinting and if that’s not burning any fat, then why bother?
Next I found that if we are to work at about 60%, our body gets half of its energy from carbohydrates and half of its energy from fat stores which is why a lot of so-called “experts” claim that you should work in the range of 60-70% maximum exertion, what we know as ‘steady-state cardio.’ However, there is so much more to it than that. What about how many calories I’m burning? You can’t lie, everyone loves to know how much energy they are expending while doing exercise! Not only does it make you feel good but it also gives you that ‘valid’ excuse for that extra slice of cake!
So if you walk off 100 calories on that treadmill, you’ve burned about 85 calories from fat stores BUT this is not as effective as spending that same amount of time at a moderate 60% run which burns off 200 calories with 100 coming from fat BUT that in turn is not as effective as spending that same amount of time doing sprint intervals that burn off 500 calories with 150 coming from fat. So in fact it is H.I.I.T that is proven the winner here but is there evidence for this? Am I really going to burn more fat if I undertake interval training rather than running at a steady pace on the treadmill for an hour?
The fact is, yes. The University of Western Ontario took 10 men and 10 women and made them train 3 times a week, one group did between 4 and 6 30-second treadmill sprints with between 4 and 6 minutes of rest in between each and in the other group did 30-60 minutes of steady-state cardio. After 6 weeks of training, the subjects doing the intervals had lost more fat!
What factors is it then that mean that high-intensity cardio is BETTER than steady-state cardio?
- Increase of metabolic rate for upwards of 24 hours after exercise
- Improved insulin sensitivity in the muscles
- Significant spikes in growth hormone levels (which aid in fat loss) and catecholamine levels (chemicals your body produces to directly induce fat mobilisation)
- Post-exercise appetite suppression
And thus the answer to the original question, ‘Is H.I.I.T the training we should be undertaking in order to burn fat?’ Yes, yes it is. The bottom line is that this high intensity interval training burns more fat in less time than steady-state cardio.