Just wanted to bury a few misunderstandings about High Intensity against Low intensity exercise and how this is being misrepresented in the popular press. First of all let me just say what I always tell my clients. I highly recommend not relying on exercise to “burn fat” to get lean. In the context of a fat loss program, exercise helps you keep your muscle, stay fit, make modest increases to your metabolism, and burn some fat. Because it’s a scientific fact that you must eat less calories than you burn to lose fat, nutrition has a much more powerful impact on this equation and consequently, it should be your main focus.
However lets look at the current trend of counting steps and the Daily Mail screaming headlines that low intensity is better that High intensity for burning fat. First of all we have to talk about the much vaunted Fat Burning Zone. This is a calculation that says take 220 which is the highest BPM of your heart, take off your age so if you are 20 this is 200 then take between 55-65% or 110 to 130 BPM. According to research if you exercise in this zone for 30 minutes you will burn 120 calories of Fat as opposed to 140 at 80% of your Max BPM. So why do HIIT for only 20 calories? Yes as usual you are only getting half the story.
At the supposed Fat burning zone you are burning 120 calories of fat but also burning 80 calories of glycogen so the total calories burned are 200. However at 80% you burn 140 calories of fat but then 260 calories of glycogen therefore you are burning a total of 400 calories!
But there is something else. The Mail also posted a set of results from a study done in the USA. Where a group of people did low intensity exercise on a bike for 3.5 minutes and burnt 29 calories where another group did HIIT and only burnt 4! There you go conclusive proof that all us HIIT speed merchants need to hand in our leg warmers and start counting our steps. But as usual they have only used half the article. This was a study about the effect of Afterburn. What the hell is this? So the full study showed that while exercising the Low intensity group did indeed burn 29 calories during the exercise, then while sitting down resting the afterburn effect of exercise kicked in and they burnt another 10 calories. So a total of 39 calories. Now the HIIT group sat down and in the same period burnt another 61 calories, so a total of 64 calories. So 95% of the calories were burnt after the exercise! Another point is the low and slow group did 3.5 minutes on the bike. The HIIT group did sprinting for 15 seconds three times. So a total of 45 seconds exercise!!!
Now obviously we have to take into account your current weight and how fit you are but just wanted to make sure you are making the right decisions about exercise based on fact not on badly written journalism.