Have We Got Metabolism All Wrong?

We burn the same number of calories regardless of lifestyle

We all know a healthy lifestyle is vital to our well-being. And yet, most of us, and much of the fitness industry, have got it wrong when it comes to losing weight by burning more calories.

Herman Pontzer, professor of Evolutionary Anthropology and Global Health at Duke University, North Carolina, has spent years studying and measuring how our modern, relatively sedentary lifestyle compares with that of our ancestors. And the results are somewhat startling.

Talking to the BBC, Pontzer said that the surprise is “we burn the same number of calories every day regardless of lifestyle.” A distant relative living as a hunter-gatherer has the same calorie cost as I do sitting at my desk for most of the day.

In his fascinating new book, Burn: The Misunderstood Science of Metabolism, he explains that gym bunnies spending endless hours working out are most likely to be burning through less energy on other stuff, such as immune functioning and other biological functions. The total calorific cost balances out.

Diet over exercise to lose weight

Despite what we may think, while those extra miles on the treadmill are essential for other areas of our health and well-being, they are unlikely to reduce our waistline. “The focus for obesity should be on diet and what we eat,” says Pontzer. And we should be avoiding ultra-processed foods because our Palaeolithic brains aren’t evolved to handle them.

Writing in the New Scientist, he says, most diet books and online workouts fail to help you lose weight due to a profound misunderstanding of how metabolism functions.

Diet and exercise just don’t work in the way that most of us have been taught. The view that our bodies are simple calorie-burning machines that we can manipulate to tone up and trim down ignores the complexity of what evolution has provided for survival and reproduction.

And, Pontzer should know. His research has taken him around the world, measuring the calories burnt by Tanzanian hunter-gatherers, Amazonian farmers, US East Coast urbanites, and even our closest furry relatives, chimpanzees, bonobos, gorillas, and orangutans.

The results led him to reject many of the metabolic myths most of us hold about how diet and exercise affect the calories we consume and use.

Yes, you do burn calories exercising. But your metabolism is more complicated than that — it is surprisingly dynamic.

When Pontzer studied adult males from the Hadza people in northern Tanzania, he found that despite logging 19,000 steps a day hunting and collecting honey, their calorific expenditure was the same as that of a typical Western sedentary office worker. It seems that regardless of lifestyle, our bodies manage to keep the number of calories burned within a reasonably narrow range.

Teaching the body to compensate

So when you start your new couch to 5k program or aerobics class, there will be an initial additional caloric burn, but before long, your metabolism will return to only a marginally higher run-rate than before you began exercising.

And that is why weight loss starts so well. Your body switches to using up any extra calories when you begin exercising but levels off over the year. Evolution has given us the capacity to fine-tune all the other tasks our bodies perform daily to compensate.

However, what it does mean is that diets do work. And according to Pontzer, it is less important which of the many diets you choose (from a weight loss perspective, rather than what is healthy). So long as you reduce your calorie intake and stick to it, you will lose weight.

Their findings also suggest that no one diet suits all.

Pontzer’s team looked at the diets of people from all over the world living very different lives, and even studying fossil and archaeological records. It turns out that humans have always had widely diverse diets. For some, it involves eating a large amount of meat, and for others, it is more plant-based.

No one is doomed to obesity

Another myth worth exploding is that for some, their metabolism dooms them to obesity.

While the amount of energy we each burn varies, it does not ultimately predict our weight. Indeed, typically an obese person has the same daily burn as a slim person. Weight gain and obesity aren’t the product of slow metabolism.

Simplifying the message

Pontzer’s message is powerful because it simple. While exercise is intensely important for mental and physical well-being, it should not be the go-to to lose weight.

As he says, “exercise won’t make us thin, but it will keep us alive.”

And there is no need to adopt the latest fad diet. Research by the US National Institute of Health confirms that a balanced diet avoiding ultra-processed is what remains crucial for our well-being and weight management.

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Psychologist in Human Performance. Writing about positive psychology and the science of mind to better understand human potential. Owner Explorethelimits.com

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