Yes, There's a Specific Age When Your Metabolism Slows Down

“I used to take pride in the fact I didn’t have to work out, and then I hit that age where you have to,” said supermodel Chrissy Teigen in an interview with Women’s Health U.K. But what is that age, exactly? (Photo: Women’s Health/John Wright)

Chrissy Teigen is nude on the latest cover of Women’s Health U.K., but the supermodel says she’s had to work hard to look that good in the buff.

“I used to take pride in the fact I didn’t have to work out, and then I hit that age where you have to,” Teigen, 29, told the magazine. Now, she says, she regularly works out for an hour so she can drink champagne, have hearty dinners, and “do what I want.”

It’s no secret that our metabolism slows as we get older, but is there an actual age or age range when it starts to go downhill?

Basically yes, says Peter LePort, MD, medical director of the MemorialCare Center for Obesity at Orange Coast Memorial Medical Center in Southern California. “It’s usually after the age of 30, but most people really notice it around 40,” he says.

Teigen is just shy of 30, though, and many people notice that their metabolism doesn’t seem to do what it used to before they even hit 30. What’s happening there?

Related: 8 Myths About Metabolism You Need to Stop Believing

According to endocrinologist Rita R. Kalyani, MD, an assistant professor of medicine at the Johns Hopkins University School of Medicine, it’s difficult to compare your metabolism in adulthood to your metabolism in puberty.

“The teenage years are a bit tricky because teenagers are undergoing … a time of increased growth,” she tells Yahoo Health. “That may be perceived as having the ability to eat more and not gain weight.”

As a result, the end of puberty (which typically happens in a person’s mid- to late teens) may lead people into thinking their metabolism isn’t working as well as it used to.

In reality, Kalyani says our metabolism changes as we get older. “As people age, they tend to gain body fat and lose muscle mass,” she says. “These changes in body composition can result in changes in the muscles’ ability to metabolize energy.” And when your muscles can’t metabolize energy efficiently, you’re more likely to gain weight.

Related: These Small Changes to Your Eating Habits Can Lead to Big Weight Loss

On a biological level, Kalyani points to research that suggests that your mitochondria (the powerhouses of your cells) don’t function as efficiently when you get older. “If there is mitochondrial dysfunction as people age, it becomes more likely that they can’t use the energy properly,” says Kalyani.

While men’s metabolisms more gradually decline with age, Kalyani says there are a few events in a woman’s life when it may change more dramatically: pregnancy and menopause.

Experts say you can’t turn back time, but you can slow the process.

Increasing the amount of exercise you do is crucial, says LePort, along with eating more lean protein and vegetables, and less junk food. “If you keep eating the same amount of food, you’ll gain weight unless you increase the exercise that you’re doing,” he says.

Exercise consistency is key too, says Kalyani. Without it, your metabolism may suffer. “As people get older, they tend not to be as physically active,” she says. “That leads to a vicious cycle. You tend to gain more fat and lose more muscle, which can further impact metabolism.”

Eat less, exercise more — sound familiar?

Read This Next: 10 Diet Mistakes Seriously Slowing Your Metabolism