A recent study published in the journal Science has shed new light on how the body’s metabolism changes over time, suggesting it peaks much earlier and declines much later than previously thought.
The landmark research, led by Herman Pontzer, associate professor of evolutionary anthropology at Duke University, examined metabolic data for more than 6,000 people ranging in age from just one week old to age 95. The largest study of its kind, it relied on data collected by an international team of scientists including research data generated at Imperial College London Diabetes Centre (ICLDC), a Mubadala Health Partner.
Results revealed that total energy expenditure is more stable for much longer than previously thought. Rather than the conventional wisdom that the body’s metabolism peaks in the teens and begins to slow around middle age, people’s total energy expenditure per kilo of bodyweight appears to peak in infancy before stabilising in their early 20s and does not change significantly until after the age of 60 when it begins to drop by about 0.7% per year. Major life events such as pregnancy and puberty were not found to have any significant effect on total energy expenditure.
Dr Nader Lessan, a consultant endocrinologist and clinical lead in research at ICLDC who contributed to the research project, says: "Combining research data from multiple centres across 29 countries is a truly novel approach and some of the findings that have already come out of this new data set are totally unexpected and quite a surprise. That total energy expenditure is stable through most of life and peaks much earlier than we thought was not a finding I expected to see. The exciting next step is to dig into why that might be and see how it informs the way we look at and treat metabolic disorders such as diabetes and obesity, including our approach here in the UAE."
The group identified four different stages of metabolism during a person’s life. After an initial surge in infancy, that sees infants burn calories 50% faster for their body size than an adult, data showed that metabolism slows by about 3% each year until a person reaches their 20s when it levels off into a new normal. Despite the commonly accepted idea that the metabolism slows in middle age, the middle decades of life were found to be the most stable of all.
Unlike previous large-scale studies that examine base metabolic rates or the amount of energy the body uses to maintain vital functions, the study looked at people’s total metabolic rate, the amount of energy they use throughout their day, walking around, working and even thinking. To do this, the research team used data from "doubly labelled water" studies, long considered the gold standard for measuring daily energy expenditure in real-life conditions. These studies have participants drink water that has had its hydrogen and oxygen atoms replaced with naturally occurring "heavy" forms and measuring how quickly they are flushed out of the body.
The study’s results and the building of a large, international data set have opened a range of new avenues for research into the metabolism and associated health conditions.
"At Imperial College London Diabetes Centre, our research is focused on the most pressing health needs of the population in the region, specifically diabetes and obesity. Having this new resource available means we will be able to supplement the research data we have already collected to build a more accurate and detailed picture and look into how it varies regionally – something that can only benefit our patients," concludes Dr Lessan.