Metabolism and our misconceptions
Like most people, until very recently, I used to think that the more I moved, the more calories I burned up. I understood that if I went on a long walk then I could probably enjoy a second slice of cake with my cup of tea afterwards, without worrying about the consequences. If I had enjoyed an indulgent weekend, then I thought I could just work harder in the gym the following week to compensate. Similarly, I believed if I exercised every day after work, then I needed to eat more than someone who did not. All these assumptions were based on a generally accepted theory that really no-one has contradicted – until now. I was shocked and fascinated when I found out that Dr Herman Pontzer had recently published his extensive research proving this theory to be wrong!
Dr Chatterjee recently interviewed Dr Herman Pontzer, an evolutionary biologist, on his “Feel Better, Live More” podcast #191. He does not focus on public health but came across some ground-breaking discoveries about our metabolism in the course of his work that really changes the way we look at diet and exercise. Realising the importance of his break-through for public health, he published the book “Burn: The Misunderstood Science of Metabolism”. For those of you who are interested to dig deeper into this fascinating subject and learn more about Dr Pontzer's work, I would highly recommend it.
However, if you just want to have a more accurate understanding of how your metabolism really works and how you can make sure you are eating and exercising in a beneficial way to improve your health and wellbeing, I am going to share some enlightening and useful facts with you.
As an evolutionary biologist, Dr Pontzer researches how our deep past has shaped the way our bodies work today. He has been doing this over the past 20 years in different settings and includes some ground-breaking field work living with the Hadza hunter-gatherers in northern Tanzania. This tribe is considered to be one of the last hunter-gatherer tribes in the world. They therefore provided a unique insight into the way we used to live.
Fascinating facts about metabolism that were discovered during this time are:
Despite the fact that the Hadza men and women get between five and ten times more physical activity every day than most men and women in the USA or Europe, their total energy expenditure (the amount of calories they burn) is the same.
Exercise does not increase our metabolism.
We burn calories within a very narrow range, namely nearly 3,000 calories per day for men and 2,400 calories for women, no matter our activity level. (This does depend on the size and muscle mass of the individual and is an average figure).
The way our body burns energy (our metabolism) effects every aspect of our biology from our pace of growth, reproduction and ageing to our weight and health.
If we burn more energy in one area, then our bodies will adjust be spending less energy in another.
Despite the fact that exercise does not increase our metabolism, we were born to move and it is essential for optimal health and wellbeing.
While this is just one evolutionary biologists’ point of view, and some people may argue against it, the evidence is certainly compelling and the science speaks for itself. It explains how people who go all out at the gym, in the pool or on their bike often fail to lose the weight they hope or expect. It explains to those who can’t lose weight through rigorous and punishing exercise regimes that they are not failures or exercising incorrectly, but that their bodies do not work the way we think they do. It is a huge breakthrough and enables us to move forward with our goals in an informed and focussed way. This theory coincides perfectly with Professor Tim Spector’s findings, explained in his book “Spoon Fed”, where he discusses the same subject in chapter 17, entitled “On your bike”, with the subtitle “Myth – exercise will make you thin”.
Here are some key quotes:
“Most of our energy expenditure is predetermined and hard to change”.
“Around 70 per cent is our pre-set resting metabolic rate, which is the energy our cells burn just staying alive”.
“Around 10 per cent of our energy is burnt off through the act of digesting food”.
“About 20 per cent for physical activity, of which around half is for small movements, fidgeting and standing. This 10 per cent expenditure amenable to change is ten times less than reducing the 100 per cent of energy that goes into your body as food”.
“Even if you manage to force yourself to the gym every day, your body will be fighting your attempts to lose weight”.
“A small amount of fat may be replaced by muscle if you are lucky, which could make you heavier, as fat is lighter, but more likely your body will compensate for the potential loss of its energy stores, which it (wrongly nowadays) perceives as dangerous. It does this by making you eat more afterwards and slightly reducing your metabolic rate short term, as well as reducing both your subconscious and conscious activity levels by making you tired.
“Rather unfairly, this compensatory mechanism appears greater in overweight people”.
As I so often find myself concluding, it is all about balance. There really are no magic bullets or quick fixes. We all need to find a good balance between diet and exercise, make sure whatever we do is not extreme and listen to our bodies. Finding a delicious, varied, balanced and unprocessed diet and combining it with regular exercise that we love, is the best way to ensure we are optimising our health and leading a happy life. For me, knowing that I can’t “run off” those extra helpings or excessive amounts of treats or snacks I might have overindulged in, really makes me think very differently and gives me a new respect for my body and the incredible way it works. It is so much smarter than we give it credit for and has been way ahead of us from the beginning of time.
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