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.

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.

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.

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. 

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.

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."

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."

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.