We’ve all heard or used the excuse one or two dozen times before: the extra weight gain is because our metabolism has slowed down! Well, according to a new breakthrough study, that’s likely not true — not until you’re 60, anyway.
The study, published last week in Science magazine, shows metabolism leveling off and staying put from ages 20 to 60.
That’s right — your metabolism doesn’t slow down past stabilization until you’re 60 years old, and then it continues to slow down.
What’s more, ladies, the study shows the stabilization in both men and women with no real differences between the metabolic rates.
According to the study, here are the four different stages of metabolism, The New York Times outlined:
There’s infancy, up until age 1, when calorie burning is at its peak, accelerating until it is 50 percent above the adult rate.
Then, from age 1 to about age 20, metabolism gradually slows by about 3 percent a year.
From age 20 to 60, it holds steady.
And, after age 60, it declines by about 0.7 percent a year.
After controlling for body size and the amount of muscle people have, researchers found no differences between men and women, the Times noted.
“It was really clear that we didn’t have a good handle on how body size affects metabolism or how aging affects metabolism,” said Dr. Herman Pontzer, an evolutionary anthropologist at Duke University behind the study. “These are basic fundamental things you’d think would have been answered 100 years ago.”
Dr. Pontzer said he was surprised to learn about infants’ metabolic rates. Babies’ metabolic rates for their first month are about the same as their mother’s, before “something kicks in and the metabolic rate takes off.”
Researchers were also surprised when they didn’t find a drop-off in women’s metabolic rate as they get into their 40s and approach menopause. “We just didn’t see that,” Dr. Pontzer said.
“There’s no effect of menopause that we can see, for example. And you know, people will say, ‘Well when I hit 30 years old, my metabolism fell apart.’ We don’t see any evidence for that, actually.’”
From ages 60-95, though, researchers found that your metabolic rate slows by about one percent each year until you die. “People thought, ‘Well, maybe it’s because you’re less active, or maybe it’s because people tend to lose muscle mass as they get into their 60s, 70s and older,’” Dr. Pontzer explained. “But we can correct for all those things. We can say, ‘No, no, no, it’s more than that.’ It’s that our cells are actually changing.”
According to the Times, the paper has more than 80 co-authors. “By combining efforts from a half dozen labs collected over 40 years, they had sufficient information to ask general questions about changes in metabolism over a lifetime,” the Times detailed the study. “All of the research centers involved in the project were studying metabolic rates with a method considered the gold standard — doubly labeled water. It involves measuring calories burned by tracking the amount of carbon dioxide a person exhales during daily activities.”
“The investigators also had participants’ heights and weights and percent body fat, which allowed them to look at fundamental metabolic rates,” the report explained. “A smaller person will burn fewer calories than a bigger person, of course, but correcting for size and percent fat, the group asked: Were their metabolisms different?”