Our bodies are built to move. In our modern, industrialised world, free of the daily demands of our ancestors, we need to exercise for our bodies to function properly. It is fundamental that movement co-exists with us. As part of our evolutionary development as a species, our bodies expect to move. If we suppress that, consequences to our health are likely.
However, we’ve grown up being told that the more we move, the more calories we will burn. But research from the field of evolutionary biology explains our deep past shaped the way our bodies work today and how this way of thinking could be wrong.
Our metabolism - the way our body burns energy - affects every aspect of our biology from our pace of growth, reproduction and ageing to our weight and health. All the work that your cells do all day, approximately 37 trillion cells, are working all day to help us function. All those tasks require energy and most of that work we are not really aware of. Did you know your brain burns 300 kcals a day!
Studies of the Hunter-gather tribes of Tanzania have found that they burn about the same amount of calories as your average, relatively sedentary person in the US and Europe, despite them generally getting between 5 and 10 times more physical activity every day.
This research suggests that independent of our activity levels, our metabolism will adjust. So if we burn more energy in one area, our bodies will spend less energy in other areas.
This implies that if you are physically active, it does not necessarily mean that you will burn more calories than someone who leads a more sedentary life and you will not increase your metabolism through exercise.
Even for someone who is exercising regularly, they are only spending less than half of their daily energy expenditure on physical activity. Most of their activity expenditure is spent on activities within their bodies that they are not even aware of. The part we are aware of are the exercise parts, when our heart rate increases, we get sweaty - so we tend to equate energy expenditure to the parts we can see and feel.
However, the body is paying attention to the levels of physical activity we do. If you suddenly increase your activity levels, start a new exercise programme, in the short-term you might lose a bit of weight early on, but over time your body will adjust to that level of activity and your total energy expenditure will moderate and not change much to what it was before.
The biggest predictor to how many calories we burn off a day is related to our size and how much fat-free mass we are made up of. The lower the mass the fewer calories we burn.
But this does not mean that you should not exercise.
Movement is essential for humans and moving our bodies has many benefits and should be incorporated as part of a holistic approach to health and wellness. For example, when we move our bodies, exercise has shown to help people keep weight off, and can assist in the regulation of hunger signals and mood.
The emphasis is on the role of exercise as weight regulation rather than weight loss. We should exercise during weight loss, for all the benefits that exercise has for the body and soul, but the science says exercise is not the key to weight loss.
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