I measured my resting heart rate using the runtastic chest strap and It is 54. I am 27 years old and my current weight is 75 kilograms (165.3 lb).

I used the Formular which according to wikipedia was the least objective to get my max heart rate:

205.8−(0.685×27) = 187.305

With this data Runtastic calculated the following heart rate zones:

Easy: 120 - 132 Fat Burning: 133 - 146 Aerobic: 147 - 159 Anaerobic: 160 - 172 Red Line: 173 - 187

But according to this image on wikipedia which uses the fox and haskell formula, my fat burning rate should be approximately 115 - 135 which is totally incoherent with the zones calculated by runtastic.

What is going on here? I know that it is not possible to say it with absolute precision, but what would my fat burning zone approximately be?

2 Answers 2


The 'fat-burning zone' is a relatively unproven idea on heart rates and fat loss. If you wanted to you can look at the two results and split the difference and aim for about 133-135. However, how accurate will your heart monitor be in practise?

If you are interested in weight loss, any substantial amount of cardiovascular activity combined with a calorie deficit will help with healthy weight loss. In fact, just a calorie defcit would work, but there are many added benefits to aerobic exercise that its well worth doing.


The "fat burning zone" is a badly misinterpreted piece of information that has somehow become written in stone among exercisers. Your body burns fat at all times during exercise, the proportion of fat to other energy sources just varies according to how intense the workout is. Additionally, while you may exercise longer at a lower intensity, the total calorie expenditure may be less than a shorter, more intense workout.

Heart rate is also somewhat unreliable as a metric to base a workout on, because there are many factors that can raise or lower the heart rate that are completely unrelated to the exercise you are doing. Dehydration and caffeine are two things that can raise the heart rate. Also, most of the "zone" charts that you see plastered on walls at health clubs are based on the atrocious concept of "220-age" being a maximum heart rate. This is one of the worst myths in health and exercise.

So as an example, say you walk on a treadmill at a heart rate of 130, and normally this a 4 mph pace. Today you are dehydrated and you drank a cup of coffee to wake up, and now the same 4 mph pace you have a heart rate of 150. You aren't working any harder or burning any more calories, but suddenly you're out of that "Fat burning zone".

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