The Myth of the Fat Burning Zone 

Why exercising in the 'fat burning zone' could be making you FATTER!  

-By Mark Woodgate

WARNING: 

This information may completely change your outlook toward fitness and fatburning!

Some myths never die. And the idea of the 'fat burning zone' is arguably one of the most misunderstood fallacies in the fitness industry today!

Let's begin by defining the theory of the "fat burning zone." The theory is that by keeping your heartrate in a zone of 50% to 65% of your maximum heart rate (which is low intensity), your body will utilise a higher percentage of your fat stores as a source of energy during the exercise period. This is actually TRUE!  But read on to find out why training in the fat burning zone may actually be making you FATTER!

The following fatburning information is VERY important!

During a cardiovascular workout, you will use two sources of energy - 1) adipose tissue (or body fat) and 2) carbohydrates. 

1) Low intensity cardio (LIT), or staying within the "fat burning zone", will produce a greater utilisation of fat compared to carbohydrate. 

2) Higher intensity cardio (HIT) will produce a greater utilisation of carbohydrate compared to fat. 

HOWEVER, lets assume that you exercise for 15 minutes using both LIT and HIT. Your total energy expenditure will be much greater using HIT cardio simply because you're exerting more effort. Relatively speaking, HIT will use a lower PERCENTAGE of fat versus carbohydrates, however, in ABSOLUTE terms and because total caloric expenditure has increased, so too has your NET fat expenditure.  As a result, your NET fat utilisation DURING exercise is actually HIGHER during HIT!

Thanks to a study by LaForge and Kosich (1995) this was demonstated as follows. For a 60 minute cardiovascular training session, using different intensities, these are the results:

As you can see - exercising at a higher intensity for a given time proved to burn more fat than at a lower intensity!  But don't be fooled by the percentages - it's the AMOUNT of fat that is important!

The fact is, you do burn more calories during a long duration low intensity cardio session compared to a short duration high intensity cardio session. But the real advantage of high intensity training is the post workout 'afterburn.' Simply put, when you exercise intensely for short periods of time you continue to burn more calories AFTER the workout has finished! 

This residual calorie burning effect can last from 24 to 48 hours - and in exercise science it is called E.P.O.C which stands for 'Excess Post- exercise Oxygen Consumption.

What this means is that your metabolism is raised for a much longer period than with a traditional LIT or "fat burning zone" workout. So, if we were to compare 60 minutes of LIT to just 15 minutes of HIT and took a snapshot of a 24 hour period, it would look something like this:

Something extraordinary happens when you train using high intensity cardio. A study at Laval University in Quebec published in a journal called 'Metabolism' back in 1994, showed that high intensity exercise burned off significantly more bodyfat than steady state endurance exercise. In this case we're not talking about calories burned during exercise, or whether they came from fat or carbohydrate, we're talking about actual fat that disappeared from actual bodies! The research concluded that: Every calorie you burn during high intensity exercise strips off 9 times more bodyfat than a calorie burned during low intensity cardio!

In other words, to come close to matching the results from a 12 minute high intensity workout, you'd have to burn off nine times as many calories using low intensity cardio!!

"Every calorie you burn during high intensity exercise strips off 9 times more bodyfat than a calorie burned during low intensity cardio!"

The reality is, you can exercise for a quarter of the time doing HIT and achieve amazing results compared to LIT ! 

Intensity is a function of the duration of your workout. In other words, the longer the workout, the less intense it will be because the body progressively fatigues the longer you train.There's a saying, 'You can either exercise for a long time OR you can train intensely...but you can't do BOTH!'

But here's the real problem with long duration, low intensity training and staying and staying in the 'fat burning zone.' Training for long periods of time produces higher concentrations of a hormone called cortisol. Cortisol promotes excessive muscle tissue breakdown and a lowered basal metabolic rate (the rate at which you burn calories.) This is why, over time, long duration low intensity training can actually make you FATTER! (especially if this is the ONLY type of exercise you do.) 

What about Fitness? High or low intensity training?

When I first began personal training in the mid 90's I came across some studies by Izumi Tabata - an exercise scientist in Japan. Dr Tabata and his team compared low intensity exercise (L.I.T.) to high intensity interval training (H.I.I.T.)

In Tabata's study, one group did a full 60 minutes of moderate-intensity exercise 5 days per week. Group two also trained 5 days a week except that this group performed up to eight 20-second sprints of high-intensity cycling with a 10-second rest (pedaling at a slower rate) in between. This was preceded by a warm up and followed by a warm down. 

Total exercise time? Just 4 minutes!

The results were extraordinary. Tabata found that athletes on the high-intensity interval training programme increased their fitness levels faster than athletes on a typical endurance training regime - despite the VAST difference in the amount of time each group spent working out. The results are as follows:

Participants in the studies who did the 4 minute workouts not only increased their ability to do anaerobic exercise (the type of exercise that features all out efforts like sprints) but also their aerobic capacity. (typically performed at a steady pace with the idea of developing endurance) Whereas group 1 showed no anaerobic fitness increase and a 10% increase in aerobic fitness, group 2 showed a 28% and 14% increase respectively..and all with only 4 minute workouts!

The one disadvantage to Tabata's protocol was that the intervals are too intense for most people. However I liked the basic idea so much that I adapted the 20 second sprint / 10 second recovery protocol and devised my own 12 and 20 minute 'Guerilla cardio' workouts. This 20 minute interval workout is now the basis of the Body Blueprint 12 Week Challenge whereby participants perform Guerilla cardio up to 3 times per week for maximum fatloss.

How Can I Add HIT to my Workouts? 

Choose a cardio machine that allows you to quickly accelerate and decelerate. For example, the elliptical trainer, rowing machine and bicycle would all be excellent choices.

Next you will choose 2 speeds that are based on YOUR level of fitness. The first represents 50% of your perceived maximum speed. The second represents 90% of your perceived maximum speed.

Start with a 2 minute warm up at your perceived 50% speed. For minutes 2-4 you would perform intervals of 20 seconds fast (your perceived 90%) and 10 seconds slow (your perceived 50%) When you reach the 4 minute mark you would then take 2 minutes of recovery and return to your original warm up speed of 50%. Depending on your level of fitness this 4 minute cycle can be repeated between 3 and 5 times.

Here is an example of H.I.I.T. (Guerilla cardio) using the elliptical trainer:                                 

nb: HIT can also be performed as a walk/ jog or jog/ sprint depending on your level of fitness. (It cannot be done on a treadmill as the short intervals do not allow sufficient time to change speeds.)

Is there still a place for traditional low intensity training? 

Yes! Especially if you're starting an exercise programme or your sport requires you to do long distance training. However, even with that in mind, I would encourage you to add high intensity interval training to your programme as soon as possible - especially if you wish to lose bodyfat as efficiently as possible, increase both your aerobic and anaerobic fitness...not to mention save many hours of unproductive cardio time! 

SAY GOODBYE TO THE 'FAT BURNING ZONE' AND WELCOME TO THE NEW ERA OF HIT FOR MAXIMUM FITNESS AND FATBURNING! 

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