What Is Metabolic Age & What Does It Mean For My Health?
You know your chronological age—the number you keep celebrating every year. But what about your metabolic age? At its foundation, metabolic age is all about how many calories your body burns at rest (or the energy your body needs to maintain its everyday functions) and how that compares to other people your age.
While chronological age is based on the number of years you lived—and you can't really do anything to change that number—a few lifestyle tweaks may help to adjust your metabolic number. Here's what to know about your metabolic age, how it affects your health, and methods for making your metabolism more efficient.
What is metabolic age?
It's tough to define metabolic age without first defining basal metabolic rate (or BMR). "Your basal metabolic rate is how much caloric energy or energy from calories you need to keep your body functioning, including the organs, digestion, muscles, and everything else working over a period of rest," explains functional medicine doctor Heather Moday, M.D. "If you were lying in bed all day long, it's what your body would need or burn in order to function." BMR is based on your gender, height, weight, lean muscle mass—and a range of other factors. The higher your BMR, the better your metabolic age.
How to calculate your metabolic age.
To calculate your metabolic age, you need to know your BMR. For that, it's best to work with a medical professional who can give you a more accurate number, says naturopathic doctor and functional medicine expert Kara Fitzgerald, N.D.
However, to get an idea of your metabolic age right now, the most common formula is one called the Mifflin St. Jeor Equation (you can find a quick calculation here):
For men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
For women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161
Once you know your BMR, you'll compare it to a metabolic age chart.
Moday says you can also get a more specific BMR by using a bioimpedance machine, which features sensors that you put on your fingers and toe. It then sends an electric charge through your body, measuring your water volume, fat, and how much your bones contribute to your weight. "People with a higher muscle mass, because they have more metabolically active tissue, require more energy to keep going compared to those with more fat," she explains. That's why it's more accurate to get a bioimpedance machine involved in calculating BMR rather than going off a formula that doesn't take into account muscle and fat mass.
What does metabolic age tell you about your health?
Lots of factors, beyond muscle and fat, can play into your metabolic age. This includes hormones and gender, Moday says. Our BMRs are typically highest when we're young, as we're growing and developing, she says, but then it drops in your 20s and continues to do so after that.
Some studies do show a link between lower BMR and some health outcomes, including age-related mortality and diabetes. Also, metabolic age relates to your metabolic health, which is a strong indicator of overall well-being. Markers of metabolic health include things like waist circumference, blood sugar, triglyceride and cholesterol levels, and blood pressure (you can read more about that here).
There is a downside to looking at BMR and metabolic age when it comes to your health, though—mainly, it's nearly impossible to compare your personal BMR to others in your age group because so many factors play a role in how many calories you burn at rest, Moday says. Your body frame and shape, your ethnicity, your genetics can all play a role.
Robin Forouton, RDN, a spokesperson for the Academy of Nutrition and Dietetics also says things like thyroid health, mitochondrial health, nutrient status, and metabolic flexibility (or how well your body transitions from a carbohydrate-burning metabolism to a fat/ketone-burning metabolism) can also play a role in BMR.
In general, your goal should be to keep your BMR revving by living an overall healthy lifestyle. Moday recommends comparing your own personal numbers over time rather than equating your body (or BMR) to other people's. "When you look at BMR, 70% is due to height and weight and genetics—that leaves about 30% of variables you can control," she explains. In other words, certain lifestyle choices may positively affect metabolic age.
Fitzgerald recently released a small pilot study with her team that found that following an eight-week program that included sleep, nutrition, and exercise components, along with relaxation techniques and supplements reduce participants' biological age by three years—showing that while you can't stop your chronological age, you can affect what's happening internally.
7 ways to improve your metabolic age.
To keep that metabolism burning and the BMR from dropping, consider these strategies for a younger metabolic age:
1. Get in more activity throughout the day.
Outside of your workouts, the activity you do at baseline each day can contribute to how many calories you burn at rest, Moday says. (This is where that 10,000- to 15,000-step goal comes into play.) Walking, jogging—any kind of aerobic activity throughout the day—will help to improve your BMR, even if that means walking around your house a little more often rather than sitting for most of the day.
2. Lift more weights.
One of the best things you can do for your BMR is strength train. "This is an intervention that is going to increase muscle mass, which improves BMR, especially as you age," says Moday, who suggests that the older you are, the more you should strength train.
3. Incorporate HIIT, too.
Working through high-intensity interval sessions will also help bolster your metabolism. One small study suggested that about four weeks of sprint interval training may increase resting metabolic rate (which is another term for basal metabolic rate) in healthy adults. "It's shorter, involves less muscle breakdown and less cortisol than long endurance training too," Moday says. Metabolic conditioning workouts will also influence the body's energy systems and often incorporate both strength and HIIT training into one session.
4. Get some sleep.
If you're not getting enough sleep, your BMR can dip, Moday says. Some research backs this up, including one study that found that those who were sleep-deprived had a harder time metabolizing fat and stored it instead, while another research paper says lack of sleep can alter glucose metabolism and the hormones that regulate metabolism.
5. Eat enough calories.
It might sound like you want to cut back on calories in order for your BMR to stay steady or rise, but you actually want to make sure you're eating appropriately for your body, Moday says. If you're eating less than your body requires, your body will likely slow down the metabolism. Foroutan agrees, saying, "Not eating enough can definitely decrease your BMR and crash metabolism."
Fitzgerald says it's also important to eat adequate protein to support lean muscle mass and avoid losing that tissue as we age. So make sure you're getting enough of the muscle-building macronutrient for your body.
6. Fill your plate with nutritious foods.
To support this health goal, Moday suggests eating a nutritious diet, filled with protein and fats, without going overboard on carbs (especially simple ones).
Besides macronutrients, though, Foroutan recommends focusing on nutrient-dense foods. "Vitamins, minerals, amino acids, and other nutrients are critical to mitochondrial health, and mitochondrial health is instrumental in turning the food you eat into cellular energy," she says. "Insufficient amounts of these nutrients can interfere with how efficiently your cells work, and that can lead to a sluggish metabolism. Iodine and selenium are also two nutrients your thyroid needs to work properly and keep your metabolism humming."
7. Control stress.
"Chronic stress is like pouring gas on the fire, where the fire is aging," Fitzgerald says. It can have a majorly negative impact on the body, including buildup inflammation, which can, in turn, lead to a lower BMR.
Metabolic age is one small part of your overall health to pay attention to, but it's definitely not the only thing you should rely on to get a glimpse of what's happening internally. It is important to be proactive about avoiding a metabolic decline, though: Metabolic rates drop as we age, but if you work to counteract that change, you'll likely be better off in terms of health, Moday says.
In general, living an overall healthy lifestyle will help you reduce your metabolic age and support metabolism. As Fitzgerald puts it: "We cannot understate the importance of good diet, stress control, exercise, and anti-inflammatory habits."
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