A declining metabolism is less common among those who are younger than 60, new evidence suggests.

Middle-aged adults can no longer blame their metabolism for triggering weight-gain, scientists claim.

Academics have revealed that adults aged between 20 and 60 tend to have a steady metabolism, with no signs of deterioration appearing until over the age of 60.

As part of the study, a team of international researchers extensively examined the metabolisms of more than 6,000 individuals from 29 different nations who were aged between eight days old and 95.

Metabolism is the chemical reaction in the body’s cells that change food into a vital source of energy that helps people move, think and grow. Overweight individuals require more energy because they have more fat for the body to manage.

According to the findings, children around the age of one have the best metabolisms – 50% greater than adults – whereas metabolisms decline annually for those over the age of 60, with it falling by 26% by the age of 90.

The results have also revealed that puberty, pregnancy and the menopause does not impact a person’s metabolism.

Senior researcher from the University of Aberdeen, Professor John Speakman said: “It is a picture we’ve never really seen before and there is a lot of surprises in it.

“The most surprising thing for me is there is no change throughout adulthood – if you are experiencing mid-life spread you can no longer blame it on a declining metabolic rate.”

Professor Herman Pontzer, from Duke University, said: “When people talk about metabolism, they think diet and exercise – but it is deeper than that, we are actually watching your body, your cells, at work.

“They are incredibly busy at one year old and when we see declines with age, we are seeing your cells stopping working.”

Professor Tom Sanders, from King’s College London, said: “Interestingly, they found very little differences in total energy expenditure between early adult life and middle age – a time when most adults in developed countries put on weight.

“These findings would support the view that the obesity epidemic is fuelled by excess food energy intake and not a decline in energy expenditure.”

The full set of results can now be accessed in the journal Science.

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