A team of international scientists published a paper in Science on how our metabolism changes over time. The comprehensive study involves:
- More than 6400 people (males and females)
- Age ranges from 8 days to 95 years old
- Participants come from 29 different countries
We burn 50-70% of our calories on the body’s vital functions. But this study takes into account today daily energy expenditure, which includes our regular activities outside of getting our bodies to function. The scientists used the doubly labeled (2H218o) water test. This is a urine test wherein the subjects drink water with tracers, which allows researchers to measure the elimination rate of C02 in the body. C02 is a by-product of metabolism.
- Infants have the highest metabolic rate, especially the first 12 months of life.
- Metabolism slows down, 3% each year after the first year, and stabilizes in our 20s to 50s. This excludes pregnancy.
- Metabolism declines after the age 60, with a gradual slowdown at 0.7% a year.
Current literature on middle-age weight gain partly attributes the experience to slower metabolism. This new study puts this belief into question. Of course, there are other biological and lifestyle aspects to consider, muscle mass, hormones, stress, less active lifestyle, in understanding why some people find it harder to shed pounds with age. But knowing that biologically, our metabolic rate remains relatively stable during middle age allows us to pinpoint better strategies if we want to understand our weight.