Does Metabolism Slow Down With Age? What the Research Shows

Updated October 25, 2026 · By the DEXASCAN.COM Team

Key takeaways

• Adult metabolism is fairly steady from about 20 to 60; the bigger decline comes after 60.
• Losing muscle is one of the strongest drivers of a lower resting metabolic rate (RMR).
• A 2026 study using DEXA found RMR still fell about 62.6 calories per day per decade after accounting for body composition.
• Measuring beats guessing: DEXA shows your muscle and fat, and an RMR test shows the calories you actually burn at rest.
• DEXA, VO2 Max and RMR testing start at $89 on DEXASCAN.COM.

"My metabolism isn't what it used to be" is one of the most common things people say once they hit their 40s and 50s, especially heading into the holidays. The real answer is more hopeful than the myth: for most adults, the slowdown happens later than expected, and a big part of it is tied to something you can change, which is how much muscle you carry.

Does your metabolism really slow down with age?

Yes, but not in your 30s or 40s the way many people assume. The biggest drop shows up after about age 60.

The best-known evidence comes from a 2021 study published in Science and summarized by Harvard Health. Researchers pooled data from 6,421 people aged 8 days to 95 years across 29 countries, measuring energy expenditure with doubly labeled water, considered the gold standard. They found:

• Ages 20 to 60: size-adjusted energy expenditure stayed stable, even during pregnancy.
• After 60: adjusted total energy expenditure and basal metabolic rate declined by about 0.7% per year.

The researchers noted wide individual variation. So while the average midlife metabolism is steady, yours may not be, and that is exactly why testing helps.

What is resting metabolic rate (RMR), and why does it drop?

Resting metabolic rate (RMR) is the number of calories your body burns at rest just to keep you alive: breathing, circulating blood, maintaining organs and tissue.

The main reason RMR drops with age is loss of lean muscle. A 2021 systematic review and meta-analysis in the Brazilian Journal of Health Review pooled 18 trials comparing older and younger adults. Older adults burned about 437 kJ (roughly 104 calories) less per day at rest. The gap was larger in men (about 725 kJ, or roughly 173 calories) than in women (about 233 kJ, or roughly 56 calories). The difference in muscle mass between groups was the factor that predicted the drop, while body weight and other body composition measures did not.

Muscle isn't the whole story, though. A May 2026 study in Experimental Gerontology measured 80 healthy adults aged 23 to 82 with DEXA for body composition and indirect calorimetry for RMR. Even after adjusting for lean mass, fat mass and sex, RMR still fell about 62.6 calories per day per decade. The authors concluded that factors beyond body composition also contribute to age-related declines. If you want to go deeper on the test itself, our guide to resting metabolic rate and how often to recheck it covers the basics.

Is it really my metabolism, or am I losing muscle?

Often it is both, and you cannot tell which from a bathroom scale. Your weight can stay the same while you quietly lose muscle and gain fat.

That is where a DEXA scan (dual-energy X-ray absorptiometry) comes in. In about 10 minutes, lying on a padded table, a DEXA scan shows:

• Body fat percentage, total and by region (arms, legs, trunk)
• Lean muscle mass by region, so you can spot imbalances or loss
• Visceral fat, the deep belly fat that surrounds your organs and is linked to metabolic risk
• Bone density
• ALMI (appendicular lean mass index), a measure of the muscle in your arms and legs relative to height and a useful marker of healthy aging. Learn more in our ALMI explainer and on our visceral fat and ALMI page.

Pairing DEXA with an RMR test answers the real question: are you burning fewer calories than a calculator predicts, and is muscle loss behind it? Our Big 3 testing page explains how DEXA, RMR and VO2 max (the maximum amount of oxygen your body can use during exercise, a key fitness marker) work together.

Can you speed up your metabolism as you get older?

You can't stop the clock, but you can protect the biggest lever you control: muscle. Because muscle mass was the factor that predicted lower RMR in the 2021 meta-analysis, keeping and building it is the most practical strategy.

• Strength train consistently. Harvard Health's summary of the Science study points to at least 150 minutes of weekly activity, including strength training.
• Eat enough protein to support muscle. See how much protein you need to keep muscle.
• Sleep 7 to 8 hours and manage stress, also part of the guidance Harvard Health highlighted.
• Don't crash diet. Aggressive cuts can cost muscle. Our 9 ways to increase your resting metabolic rate offers practical ideas.

Women in midlife often notice changes in where fat is stored, too. If that sounds familiar, read why belly fat increases during menopause.

What to do next

1. Book an RMR test to learn the calories you actually burn at rest.
2. Get a baseline DEXA scan to see your muscle, fat, visceral fat and ALMI.
3. Build a plan around strength training, protein and sleep.
4. Rescan every 8 to 12 weeks at the same location so your results are comparable and you can see whether you're keeping muscle.

Want a goal to train toward this season? Take a look at the Holiday Body Challenge registration bundle.

Frequently asked questions

At what age does metabolism slow down?

A 2021 study in Science of 6,421 people found size-adjusted metabolism was stable from about age 20 to 60. After 60, it declined about 0.7% per year. Individual results vary, which is why an RMR test is useful.

Why does metabolism slow down with age?

Loss of muscle is a major driver. A 2021 meta-analysis of 18 trials found the difference in muscle mass predicted lower resting metabolic rate in older adults. A 2026 study suggests other factors beyond body composition also play a role.

How can I tell if I'm losing muscle as I age?

A DEXA scan measures lean muscle by region, body fat percentage, visceral fat and ALMI in about 10 minutes. Comparing scans over time at the same location shows whether you are keeping or losing muscle.

How much does an RMR test or DEXA scan cost?

On DEXASCAN.COM, DEXA, VO2 Max and RMR testing start at $89. Prices are shown upfront for each validated provider, and you can buy online and get booking instructions within minutes.

How often should I check my body composition and metabolism?

A common approach is a baseline DEXA scan, then rescanning every 8 to 12 weeks at the same location while you work on a plan. Retesting RMR after meaningful changes in weight or muscle can help update your calorie targets.

Is a DEXA scan safe?

A DEXA body composition scan uses low-dose X-rays and takes about 10 minutes while you lie still on a padded table. Our guide to DEXA scan radiation explains the details, and you should talk with your provider first if you are pregnant or have questions.

Related reading

• The Complete Guide to RMR Testing in 2026
• Why Did My DEXA Scan Say I Lost Muscle?
• Is a DEXA Scan Safe? Radiation Explained

Find a DEXA scan near you

DEXASCAN.COM validates its providers, shows prices upfront, and lets you buy online and get booking instructions within minutes. DEXA, VO2 Max and RMR testing start at $89. Have questions about metabolic testing first? See our RMR testing FAQs.

Find a DEXA scan near you →

Sources: Harvard Health Publishing, "Surprising findings about metabolism and age" (2021), summarizing a 2021 study in Science; Moliné et al., "Effects of body composition on age- and sex-related differences in resting metabolic rate from a healthy aging cohort," Experimental Gerontology (2026); "Effects of aging on resting metabolic rate: A systematic review and meta-analysis," Brazilian Journal of Health Review (2021).

This article is for educational purposes and is not medical advice. Talk with your healthcare provider before starting or changing any medication, diet or exercise program.