Metabolism peaks at age one and tanks after 60, study finds

A study of 6,400 people from eight days old up to age 95 in 29 countries suggests the metabolism remains "rock solid" throughout mid-life.

The study, published in the journal Science, found four phases of metabolic life:

• Birth to age one, when the metabolism shifts from being the same as the mother's to a lifetime high 50% above that of adults;
• A gentle slowdown until the age of 20, with no spike during all the changes of puberty;
• No change at all between the ages of 20 and 60;
• A permanent decline, with yearly falls that, by 90, leave metabolism 26% lower than in mid-life.

Thus it peaks at the age of one, is stable from 20 to 60 and then inexorably declines. There is no change throughout adulthood. And so if you are experiencing mid-life spread, you can no longer blame it on a declining metabolic rate. And there was no metabolic surge during either puberty or pregnancy and no slowdown around the menopause. 

The high metabolism in the first years of life also emphasizes how important a moment it is in development and why childhood malnutrition can have lifelong consequences. 

The researchers said fully understanding the shifting metabolism could have implications in medicine. For example, Prof Pontzer from Duke University said it could help reveal whether cancers spread differently as the metabolism changes and if drug doses could be adjusted during different phases. 

And there is even discussion about whether drugs that modify the metabolism could slow diseases of old age.

And it "cannot be a coincidence" diseases of old age kicked in as the metabolism fell.

Prof 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."