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21 Apr 2006

how can i make sure i'm burning fat on the treadmill?
Hi i've started cardio and 2-3 times a week do 40 mins being 15 mins on the stepper and 25 walking on the treadmill. On both machines i up the pace every 5 mins so its quite fast towards the end. I'm now not sure this is how i shd be doing it to maximise burning of fats. Is there a recommended way. Some ppl say u slow down then go very fast then slow down then fast again etc. Others say a mid-paced speed the whole way thru, no variation. Others do it the way i do, start off at a manageable pace and get quicker and quicker.


purely from a fat burning perspective, what shd i be doing? PS I'm a good weight for my height, i'm 53.5 - 54kg at 168cm and all i'm trying to do is tighten up my body by toning up and removing the superfluous layer of fat, its not for weight loss as such. I'm the same weight after i had a baby 3 yrs ago but i just feel a lot softer.


thanks, any advice appreciated


jenna
Answer 403 views
Expert
FitnessDoc
fitnessdoc

01 Jan 0001

Hi Jenna

The whole issue of burning fat is shrouded in mystery, unfortunately, and so I hope that I can clear up some of the issues for you.

The bottom line is that there is no simple way to turn on the body's fat burning mechanism. This is because the body does not have one! The body does not use fat and then carbs, or carbs and then fat, it uses them all together, except the relative intensity that you train at determines how much of one contributes to your energy requirements. And that means that the key is to ask what you need to do to burn the most fat in TOTAL, rather than trying to burn fat instead of carbs.

Perhaps this is easiest illustrated if I use the relationship between heart rate and exercise intensity.Ever since people noticed that heart rate goes up as intensity goes up, they have used it to gauge exercise intensity. Then, when it was noticed that the fuel that is used also depends on the exercise intensity, it was thought that heart rate monitoring was a good way to train at just the right zone to burn fat. In theory, this is true, but there is more to it than this. What happens is that at low exercise intensities (less than 60% of maximum), the main source of fuel used by the body is fat. As exercise intensity increases above 65 to 70%, progressively more and more of the energy that is produced comes from the carbohydrate stores, meaning that fat contributes a smaller overall percentage of the total energy use. However, and many people forget this, the overall energy use also increases, so that, even though fat might be contributing less as a percentage of the energy, it is still being used in larger quantities. That means that the total amount of fat being burned per minute might actually be higher at higher intensities, which is what you want. So, many people make the mistake of trying to go at a low intensity, to burn fat, which means that they are probably using more fat than carbohydrate, but the overall energy used is so low that the results are barely noticeable.

SO, basically, the body does not have certain ‘zones’ at which it uses just fat and then just carbohydrates – there is no on-off switch, but a gradual change from fat to carbohydrates, which means that you have to find the exact intensity to burn more fat in total, not more fat as a percentage, if you follow my logic. Also, at slightly higher exercise intensities, the total energy that is being used is greater, which means that the total amount of fat that is being used is also greater – so, to answer the question, I’m more in favour of higher intensity training to burn fat. However, a word of caution, this does not mean going out and training hard all the time. You have to find the right balance. Your goal should be to use the greatest total amounts of fat, and this means that the duration of the training must also be long enough to burn more fat. So, it’s not only the intensity, but also the duration that is vital. That’s why you can’t just go out and train at 90% of maximum – you would tire very quickly, meaning that your total fat and energy use would be relatively low.

Therefore, my advice would be to aim for an intensity between 70 and 80% of maximum. In your case, anything between 150 and 175 bpm would probably be about right – the main thing is to be able to finish a session of 45 minutes or so of training feeling like your breathing is elevated, that you’ve had a hard session, but that you are not completely exhausted. If you want to go fast and slow and mix up your running speed, that is fine too, but the key is to maximize training time and the high intensity that burns the most energy.

Good luck
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