The New Science of Metabolism

In this The Guardian article, David Cox quoting findings from a Science article writes that challenged one of the universal truths of our body metabolism. “For decades, scientists have accepted that metabolism begins to slow down in early adulthood, initiating a steady descent that continues through middle age and later life, inevitably resulting in the phenomenon known as ‘middle-aged spread‘.”

According to Herman Pontzer, the lead author and an associate professor of evolutionary anthropology at Duke University, North Carolina, and more than 80 other scientists have compiled data from more than 6,400 individuals – from eight days to 95 years old – reported something different in their Science article.

It appears that between the ages of 20 and 60 our metabolism stays almost completely stable, even during major hormonal shifts such as pregnancy and menopause. Based on the new data, a woman of 50 will burn calories just as effectively as a woman of 20.

The Science study showed that infants burn energy at such a rate to support their development that their metabolism at one year old is more than 50% higher than an adult’s. The second transition takes place at about the age of 60, when our metabolism begins to drop again, continuing to do so until we die.

Explaining the study’s finding The Guardian writes:

Much of the ageing process, and the commonly observed middle-aged weight gain, is not because of declining metabolism but genetics, hormone changes and lifestyle factors such as stress, sleep, smoking and, perhaps most crucially, diet. Pontzer argues that if the calories we burn stay largely the same throughout life, then the real source of obesity has to be the amount we’re eating, and particularly the heavy consumption of highly processed foods.

Dr Pontzer told “I think there is a deep evolutionary reason to this. In the industrialised world, burning more energy than you eat would be great, but in the wild, that’s a bad strategy. The reason we’re gaining weight is not only because there’s more food available than we have evolved to expect, but because they’re modern, industrialised foods, designed to be overeaten. So you’ve got this perfect storm for making people obese.”