Science Says Your Metabolism Doesn't Actually Slow Down as Soon as You Think It Does

As we mature in age, our bodies feel the effects. However, the functions we often associate with youth, like metabolism (which measure the rate of your body's caloric burn), don't necessarily slow down as soon as you think they do. According to Good News Network, a new study revealed that your metabolism actually begins to decline later than mid-life (in your 40s and 50s), which was previously widely accepted as the turning point.

To come to these findings, scientists from Duke University studied 6,600 people from one week in age to 95 years of age in 29 different countries around the world. Herman Pontzer, an associate professor at Duke University, the study co-author, and the author of Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy ($20.49, amazon.com) found the results surprising after analyzing data during his subjects' puberty and menopause phases, factoring in other health-related elements. "What's weird is that the timing of our 'metabolic life stages' doesn't seem to match those typical milestones," Pontzer said.

Previous studies detailed how the body uses energy to carry out daily functions, like breathing, digesting, and pumping blood. However, these tasks only account for 50 to 70 percent of the calories we burn in the everyday. This study took measured other burn-inducing patterns, like washing dishes, exercising, or walking the dog. The team used the "doubly labeled water" method (a urine test after drinking water with natural "heavy" forms of water molecules) to understand the total amount amount of energy participants burned each day; they then measured how these molecules were flushed out of their systems.

The results? The researchers found that babies burn calories about 50 percent faster than adults. "Of course, they're growing, but even once you control for that, their energy expenditures are rocketing up higher than you'd expect for their body size and composition," Pontzer said. By our 20s, energy slows by three percent. The biggest finding, however, was that during our 20s, 30s, 40s and 50s, caloric burn is the most stable. Metabolism ultimately declines after the age of 60 (not before!) due to a decrease in muscle mass and cellular slow-down. "All of this points to the conclusion that tissue metabolism, the work that the cells are doing, is changing over the course of the lifespan in ways we haven't fully appreciated before," Pontzer said. "You really need a big data set like this to get at those questions."