Metabolic Age: What Is It and How to Improve It

They say age is less about the number and more about how you feel. Some things will inevitably change as we age, but that doesn't mean we can't age gracefully and healthily. Aging well means continuing to do what you love without letting your age get in the way.

Theories of aging and disease are complex, but one emerging principle is the role of metabolism in health and longevity. Metabolism is the set of chemical reactions that occur in living cells to maintain life, and it typically slows down as we age. Cellular aging is linked to changes in metabolic health, which is why scientists are interested in studying metabolic rate as a marker of health.

So, where does metabolic age come in? Metabolic age measures how fast or slow one's metabolism is relative to others of the same chronological age. 

But is metabolic age something we can measure and track? And if so, what does it reveal about our health? Let's take a closer look.

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What Is Metabolic Age?

Chronological age is the number of years you've been alive, while metabolic age measures how well your metabolism functions compared to other people at the same age.¹

A higher metabolic age means someone's metabolic rate is lower than expected for their age. Your doctor will not necessarily check metabolic age, and it's not used for diagnosis. The fitness community more often uses it to assess overall health and fitness.

In some cases, metabolic age could be a helpful tool to track metabolic health and make lifestyle changes accordingly. Still, getting the number is not always easy (stay tuned for more on calculating metabolic age).

Metabolic Age vs. Chronological Age

Your chronological age, or your actual age, measures the number of calendar years that have passed since you were born. It’s a standardized way to measure your age, giving you a frame of reference to gauge your fitness level and health goals against peers your age.

Your metabolic age, on the other hand, measures your basal metabolic rate and compares it to those of others in your age group. Although it’s not always the case, a metabolic age lower than your chronological age is often a result of many healthy lifestyle habits. When your metabolic age exceeds your chronological age, changes to your dietary intake and workout routine may help close the gap.

Basal Metabolic Rate and Health

To better understand metabolic age, it's helpful to think about it as another way of examining your metabolic rate.

The number of calories your body burns at rest (outside of physical activity level) is known as your resting energy expenditure. But your basal metabolic rate (BMR), sometimes called resting metabolic rate (RMR), is the number of calories your body needs to maintain vital functions such as breathing, heartbeat, and cell growth. This energy expenditure can vary depending on age, gender, lean muscle mass, genetics, and more.

Some research suggests a person's average BMR is an important marker for metabolic health. A lower BMR is associated with an increased risk for metabolic health conditions like diabetes, cardiovascular disease, and insulin resistance.² 

On the other hand, a higher BMR may also be inversely associated with all-cause mortality, based on the results of another study.³ In other words, a higher metabolic rate is linked to living longer.

What Your Metabolic Age Tells You About Your Health

Let's say you can measure your metabolic age. What can it tell you? A lower metabolic age means your metabolism is functioning at a level comparable to people younger than you chronologically.⁶ 

Of course, many factors affect metabolism besides age, including muscle mass versus body fat mass, weight, hormones, and genetics. So, your metabolic age isn't necessarily a perfect reflection of your health. 

But what does science say? There isn't much research on metabolic age, but a few interesting studies exist. One study that assessed metabolic age as a predictor of heart disease found that people with higher metabolic age have a higher risk of developing heart disease.⁶

Some research has also found an interesting correlation between high metabolic age and a higher risk of developing metabolic syndrome.¹

Metabolic syndrome refers to a group of conditions like insulin resistance, high waist circumference, high blood pressure, and high cholesterol that increase the risk for chronic disease. 

Scientists also found that younger metabolic age is associated with lower body weight, BMI, systolic blood pressure, and waist circumference.⁷

Considering this, metabolic age could be a marker for metabolic health—but it's not the only way to measure it.

Your Basal Metabolic Rate Changes With Age

Recent research suggests that metabolism drops regardless of body size as we age. Scientists discovered four significant phases of metabolic rate change in life. Up to age one, metabolic rate is high, but once a child hits their first birthday, it drops by nearly 3 percent a year until age 20.⁴

No significant changes occur from your 20s through your 50s, but once you reach 60, your metabolic rate drops by under one percent a year. In this study, the metabolic rate varied within each age group—meaning two people at a certain age could have very different rates. But the overall declining pattern remained the same for everyone even after controlling for things like body weight.

What does this mean? It means that some changes to metabolic rate are inevitable with age, so keeping your metabolism as healthy as possible is essential to offset these changes.

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How to Calculate Your Metabolic Age

The truth is that it's challenging to calculate metabolic age on your own because the most accurate measures of BMR require special equipment that's not readily available. 

You can estimate your BMR using calculations like the Harris-Benedict equation that considers age, gender, height, and weight (there are many online calculators, so you don't have to do it by hand). But unfortunately, even experts admit that these predictive equations are moderately accurate at best and lead to many errors in estimating someone's actual metabolic rate.⁵

An accurate method for measuring BMR is indirect calorimetry, which involves wearing a mask connected to a machine. The machine measures the amount of oxygen you inhale and the carbon dioxide you exhale to estimate your BMR. But many people don’t have access to this machine.

In reality, metabolic age isn't quite ready for primetime as a significant marker of health and body functioning. That said, if you have access to metabolic testing, it could be an exciting piece of information to track.

Factors That Increase Metabolic Age

We've established that metabolic age isn't an easy number to track. But let's consider that metabolic age is a reflection of metabolic health. It makes sense that certain lifestyle factors would increase or decrease metabolism (and therefore metabolic age), such as:

• Nutritionally Poor Diet: Specific diet patterns (think highly processed carbohydrates without fruits, veggies, whole grains, healthy fat, and protein) can adversely affect metabolic health.
• Lack of Exercise: Exercise helps to increase muscle mass, which can boost metabolism. It also helps to improve insulin sensitivity and reduce inflammation.⁸
• Stress: Chronic stress can lead to weight gain, insulin resistance, and inflammation.⁹
• Crash Diets: Surprised to see this here? Drastically cutting calories or jumping on and off the latest restrictive diet can backfire by slowing your metabolism. These diets don't work, aren't personalized to you, and aren't sustainable long-term. Carbs aren’t the enemy.

6 Ways to Decrease Your Metabolic Age

On the other hand, some factors can improve metabolism, translating to lower metabolic age and better metabolic health. While there’s no one-size-fits-all way to decrease metabolic age, certain lifestyle habits can support a healthy BMR.

Ways to decrease metabolic age include:

• Regular Exercise: Combining aerobic exercise and strength training has been shown to increase muscle mass, which can improve metabolic rate.¹² As we age, muscle mass begins to decline, accelerating the drop in metabolic rate. This is why it's important to strength train as we age to help preserve muscle mass (and metabolic rate).¹⁰
• Eat Enough Protein: Protein is essential for maintaining muscle mass, especially as we age. Try to include protein at every meal—chicken, fish, lentils, eggs, yogurt, cottage cheese, and beans are all good options. A registered dietitian nutritionist can help you understand your individualized protein needs based on your body’s demands and medical history.
• Get Adequate Sleep: Sleep is crucial for overall health, including metabolism. Sleep deprivation can alter metabolic rate, increase the risk of type 2 diabetes, and adversely impact hormones.¹¹
• Manage Stress Levels: Self-care and stress management are significant in maintaining a healthy metabolic age. Stress management doesn't have to be meditation or journalling—it just needs to bring calm and joy to your life. If the idea of stress management stresses you out, keep it simple. Call a best friend, laugh with your kids, or have a dance party in the living room. Find what works for you.
• Trying Medical Weight Loss Programs: Unfortunately, excess weight can increase the risk of developing metabolic syndrome.¹⁴ Sustainable weight loss under the guidance of a healthcare professional may be an appropriate way to decrease metabolic age and improve metabolic health.
• Increasing Insulin Sensitivity: While more research is needed to understand its effects, impaired insulin sensitivity has been linked to aging.¹³ Managing blood sugar levels can help support healthy aging.

Will Losing Weight Improve Metabolic Age?

Losing weight doesn't automatically improve metabolic age. But it could.

If you lose weight in a healthy way—eating nutritious foods, exercising regularly, and managing stress—metabolic age could improve by increasing lean body mass and improving insulin sensitivity. 

But more importantly, healthy lifestyle changes that naturally support weight loss can improve overall metabolic health, which is likely a better marker of health.

On the flip side, if you lose weight in an unhealthy way—crash dieting or yo-yo diets—metabolic age could increase as your metabolism slows down.

Metabolic Age: Is It Important?

After reading the above, you may wonder if metabolic age is actually an important number. 

Not necessarily. If you have access to tools to accurately evaluate your BMR, it could be a way to assess your health. However, markers of metabolic health like insulin resistance, inflammation, and body composition are likely more important. 

That said, there's no harm in tracking metabolic age to motivate yourself to live a healthier lifestyle and reduce your risk of chronic health problems. Lifestyle choices that improve metabolic health—eating nutritious foods, exercising regularly, getting enough sleep, and managing stress—will also help improve metabolic age and overall well-being. 

Keep the focus on making healthy lifestyle choices, and you'll set yourself up for better metabolic health at any age.

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