You head to the gym. You work out on machines such as the treadmill, upright cycle, or stepper. As you do so, you notice different exercise zones labelled ‘maximum fat burning’, ‘maximum cardio benefit’, and other variations. You may even have been intrigued by these seemingly irrelevant distinctions (or not, as the case may be!) because surely all aerobic exercise, done for a long enough period, is fat-burning!

Congratulations, you’ve stumbled upon one of the great misconceptions of exercise, that of the low-intensity ‘fat burning zone’,  arguably the most misunderstood fallacy in the health and fitness world today. Put simply, you’re being told that you’ll lose body fat more efficiently by working out in the fat-burning zone—doing your aerobic workouts at a low, rather than high, intensity

Why is it plastered all over the gym? Proponents of the zone argue that it represents a kind of exercise sweet spot—typically between 60 and 70 per cent of our maximum heart rate—in which our body burns most fat

So, should you buy into the idea?

In a word—NO

How did the myth begin and grow?

It all started a few years back when exercise scientists discovered that the higher the intensity of the exercise, the smaller the percentage fat provides of total calories burned. So, at an exercise intensity of 69% of maximum heart rate, fat provides about 50% of the calories you need to keep going for the first hour. At an intensity of 85% of maximum heart rate, fat provides about 33% of the calories you need

In a classic case of everything getting lost in translation, ‘send reinforcements we’re going to advance’ quickly became ‘send three and fourpence, we’re going to a dance’. The finding metamorphosed into the theory that the best way to lose fat is low-intensity aerobic exercise, and in the blink of an eye, this led personal trainers, exercise organisations and fitness gurus to promote low-intensity aerobic training as the ideal way to lose fat. The notion that you could work out less intensely and apparently burn more fat seems like manna from heaven in today’s ‘something for nothing’ society

While it IS true that a higher proportion of calories burned during low-intensity exercise come from fat (about 60 per cent as opposed to approximately 35 per cent from high-intensity programs), high-intensity exercise still burns more calories from fat in the final analysis

Here’s the most obvious flaw in the argument—if you take ‘low intensity’ to its logical conclusion, you could say that sleeping for twelve hours a day is the ultimate fat burner because when you’re sleeping (a very low-intensity activity indeed), you’re burning the greatest proportion of fat to carbohydrates!

The Tortoise and the Hare

Let’s look at the theory in terms of the classic fable of the tortoise and the hare. Running burns about 100 calories per mile, so let’s assume the hare’s doing 8 mph and the tortoise 4 mph. In 30 minutes the hare will travel 4 miles and burn 400 calories. In the same period the tortoise will go 2 miles and burn 200 calories

Strike one against the tortoise

Generally speaking you burn about 60% of calories from fat at an ‘easy’ intensity and 35% from a ‘high’ intensity. The hare will burn around 135 calories from fat, while the tortoise will burn around 120 calories from fat

Strike two against the tortoise

Building muscle is key to burning calories.. The tortoise’s slow pace doesn’t require much muscle power. The faster you move, the more your body responds by building muscle. The hare’s moving faster so it’s strike 3 and out against the tortoise!

The truth

As usual, if something seems to be too good to be true, then it almost certainly is! What’s happened is that, in their rush to give the public the apparition of something for nothing, the gurus, the trainers and the authors all either failed to recognise, or conveniently ignored the crucial distinction between percentage values and absolute values

This is the part of the truth that’s either misunderstood or ignored by the something for nothing brigade – high intensity exercise does use a smaller percentage of fat, but it also leads to a larger total number of calories burned. Put another way a small part (smaller percentage of fat per calorie at a higher intensity) of a big pie (more total calories burned) can be just as big or bigger than a larger piece (bigger percentage of fat per calorie at a lower intensity) of a smaller pie (fewer total calories burned)

Bear in mind that you lose weight and body fat when you expend more calories than you consume, not because you burn fat (or anything else) when you exercise

Of course, the less intense form of exercise has its benefits as well. For example, because many overweight people tend to find that lower-intensity exercise is more comfortable, they may, therefore, be willing to engage in such workouts. The point to remember is that low-intensity workouts do, in fact, promote weight and fat loss. You just have to do them for a longer period of time

The bottom line? The idea that there’s some kind of magic zone whereby you exercise less intensely, don’t increase the length of your workout, and somehow burn more fat is, sadly, false

Interval Training

There is nothing wrong with integrating some ‘fat burning zone’ sessions into your training schedule alongside other forms of exercise, such as strength training and interval workouts. Doing so can  provide a well-rounded approach to fitness, addressing different aspects of performance and health. Just don’t do them exclusively

So, is there a better way of performing cardio workouts to improve fat loss results? Yes. This is done through interval training.

Interval training refers to a series of intense activity separated by short rest periods. Utilising interval training will eventually enable you to exercise at a higher overall intensity without getting as tired. This occurs because you alternate periods of high intensity exercise with periods of lower intensity, allowing you to do more work in the same time period than you could before

The benefits of interval training lie in the fact that as you improve, the work intervals can be made increasingly harder, recovery intervals can be shortened or training can be performed at a higher speed. Like weight training, there’s no limit to the improvement you can make in your fitness