New research shows we were wrong about metabolism all this time. You probably know that once your reach your 20′ the metabolism slows down, and your body gains a few more kilos. However, according to the latest study, there are four periods of life that affect metabolism.
Experts from Duke University conducted a study based on the data from 6,500 people ranging from 8 days to 95 years. The results show no significant difference between men and women regarding metabolism once you control a few factors.
“There are lots of physiological changes that come with growing up and getting older,” study co-author Herman Pontzer, an associate at Duke University, said in a press statement. “Think puberty, menopause, other phases of life. What’s weird is that the timing of our ‘metabolic life stages’ doesn’t seem to match those typical milestones.”
Scientists analyzed how many calories a group of people from 29 countries burn each day. However, compared to the previous studies, experts tested the urine to determine the daily energy expenditure. Known as “doubly labeled water”, the test involves drinking water with naturally occurring heavy forms instead of hydrogen and oxygen. The measurement is based on how fast they flush out.
“By calculating how much hydrogen you lose per day, and how much oxygen you lose per day, we can calculate how much carbon dioxide your body produces every day,” Pontzer explained. “And that’s a very precise measurement of how many calories you burn every day, because you can’t burn calories without making carbon dioxide.”
According to the results, a newborn needs a lot of energy in the first 12 months of life. By the first year, the baby burns calories 50% faster than an adult. However, an infant also triples its body weight. Why is that, is still unknown to scientists. The cells inside the baby are more active despite their small size.
Another finding shows that metabolism slows down by 3% each year until our 20′. Energy expenditures in our 30′ are more stable despite the common knowledge. According to the study, metabolism is not a cause for our thick waistline. Surprisingly, metabolism only slows down after our 60′. Energy expenditures slow down by 0.7% every year.
The research shows that in our 90′ we need 26% fewer calories every day. The reason seems to be the loss of muscle mass. However, experts don’t have enough data to be 100% sure. As we grow older, we lose muscle mass, meaning we won’t burn as many calories as in midlife.