A sluggish metabolism is a common scapegoat for the unwanted changes in body composition and fat distribution that can come with age. But just how much does aging affect the efficiency of your body’s engine? And is there anything you can do about it?
We tapped three experts in fitness, nutrition, metabolism, and aging to break down what you need to know to support your metabolism at any age.
What is metabolism?
Metabolism is the body’s ability to take in fuel and process it to support life.
“It consists of all the complex biochemical reactions that go on in the body to create energy in order to survive,” says fitness and nutrition educator and researcher Mike T. Nelson, PhD.
Energy expenditure is measured in calories. Your total daily energy expenditure (TDEE) has four components.
1. Resting metabolic rate (RMR) measures the calories you burn at rest. This figure accounts for approximately 60 to 70 percent of calorie-burning processes and is most influenced by your body mass and composition.
2. Thermic effect of food (TEF) represents the calories you burn to digest, absorb, and process food. TEF makes up about 10 percent of daily calorie burn for adults eating a diverse and balanced diet.
3. Nonexercise activity thermogenesis (NEAT) refers to the calories you burn moving around as part of everyday life. “The biggest factor you can change when it comes to metabolism is increasing your NEAT,” says Nelson.
Making everyday things a little bit harder for yourself adds up: taking the stairs instead of the elevator; walking or biking for part of your commute; using a standing or treadmill desk; or storing items you commonly use on a harder-to-reach shelf or cabinet.
4. Formal exercise triggers the calories you burn doing a workout, sport, or other physical activity. This is typically a smaller piece of the TDEE pie, but it’s highly important for metabolic health, says certified fitness coach Paul Kriegler, RD, CPT, CISSN, Life Time’s director of nutritional product development.
“It’s important to understand that your metabolic rate is a measure of how busy your cells are,” adds Herman Pontzer, PhD, a metabolism researcher and professor at Duke University. “We’re really aware of the calories that our muscle cells use during exercise, but all of your organs — not just your muscles — are burning energy all day.”
Is a slowdown inevitable?
Despite popular belief, metabolism doesn’t suddenly tank when we turn 30, 40, or even 50.
Pontzer led a study in 2021, published in the journal Science, that created a road map of how metabolism changes over a person’s lifespan. “What we see is that it’s quite stable from your mid 20s through your late 50s,” he says. “But then starting at about 60 years old, it starts to decline pretty steadily.” (Learn more at “Metabolism Changes With Age — Just Not When You Might Think.”)
Still, chronological age does not singularly determine metabolic function, experts say. Changes in lifestyle have a profound effect.
“My biased opinion, and the answer that nobody wants to hear,” Nelson says, “is that people generally don’t move as much as they get older — specifically movement that’s not formal exercise.”
Do changes vary by gender?
Not really. While conventional wisdom has it that women experience a sharper decline in metabolic rate because of the menopause transition, research suggests this is not the case.
“We looked at data from thousands of men and women and expected to see a change in metabolism around the time of menopause in women,” Pontzer says. “But in fact, both men and women are really steady in their metabolic rate through their 40s and 50s.”
That’s not to say the menopausal shift isn’t significant for metabolic health. Age-related declines in sex hormones can alter how fat is stored in the body. More visceral fat deep in the abdomen can also create a cascade of health issues, including metabolic dysfunction. (Learn more at “5 Questions About Visceral Fat and Aging — Answered.”)
Additionally, hormonal changes “can definitely affect how you feel and make you less inclined to exercise or move,” says Pontzer. “And if it’s harder for you to keep active and keep your lean mass up, then these things can have an effect on your metabolism.”
What’s the best exercise to support metabolism?
“Exercises that help you build or maintain your muscle mass are a particularly good idea,” says Pontzer.
Nelson recommends doing two or three full-body weight-training sessions each week, plus two or three days of an enjoyable aerobic activity. If you’re new to exercise, build up to this schedule gradually, and consider enlisting the support of a trainer to help you get started without risking injury or overtraining. (For a longevity-focused training plan, visit “How to Make a Fitness Plan Based on Your Goals.”)
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