When Does Your Metabolism Slow Down? Dietitians Weigh In

If you've noticed changes in your body recently, it's likely you're just experiencing the natural progression of aging. Your body at 30 isn't going to look like your body at 20, and so on—and it's not supposed to! Your cells and organs are constantly evolving, and whatever is happening on the inside will often affect how we look on the outside. 

When it comes to physical changes, people often wonder if their metabolism is playing a part in their body composition—especially as they age. So, we asked experts in the space to break down when metabolism slows down, what causes the metabolism to slow down, and what you can do to help it stay active. 

Registered dietitian and certified intuitive eating counselor Courtney Vickery, M.S., R.D., L.D., defines metabolism as the processes that occur in the body to create the energy used to help our body "perform even the most basic functions." Everything from breathing to maintaining homeostasis with our body temperature circles back to a healthy metabolism, and it starts, Vickery says, with the food you eat. 

Vickery tells mindbodygreen that while it was originally believed that a person's metabolism would begin slowing down at the age of 30 (in increments of 2% to 5% per decade), "recent studies have shown this may not be the case." 

According to a 2021 Science review, metabolism stays pretty consistent1 throughout your life: The findings suggest that, initially, the metabolism of a newborn is akin to that of an adult but increases in the first year of life. From there, metabolism is thought to "gradually decline" until age 20 and maintain its speed through age 60. 

But again, your metabolism doesn't plummet when the clock strikes midnight on your 60th birthday. After 60, the total energy expenditure and BMR of the study's participants only declined by 0.7% per year, which suggests that metabolism doesn't drastically slow down with age. 

Generally speaking, there's no definitive age at which every human body's metabolism will start to slow down, nor does it happen dramatically. That said, a person's metabolism can significantly slow down as a result of hormonal or energetic fluctuations, nutrient deficiency, loss of muscle mass, or a higher burden of toxin exposure. 

According to Kyrin Dunston, M.D., FACOG, a board-certified OB/GYN with fellowship training in anti-aging, metabolic, and functional medicine, you should seek an assessment from a professional health care provider if you notice a drastic shift in your metabolism in your 20s or 30s "to prevent further complications down the line" and improve your metabolic health. This should also be a person's first course of action should they notice their metabolism has significantly sped up. Vickery warns metabolic health changes can be caused by an underlying culprit (e.g., thyroid issues) and can have "unwanted consequences on the body if left unaddressed."

In the same way that your metabolism won't drastically dip overnight, there will also be clear signs over time that your metabolism is beginning to slow down. The key is to take note of these telltale signs now so that you're aware and able to contact your health care provider for further assessment. 

Here, Vickery lists seven ways to know your metabolism is slowing down:

If you experience one or more of these side effects, you should seek assistance from your health care provider, as there are tests they can run to determine if your metabolism is considered slow, fast, or just right. Some methods Vickery is most familiar with are the glucose tolerance test (GTT), which determines your body's ability to process glucose; the thyroid function test (TFT), which detects issues with the thyroid; the VO₂ max test, which measures how much oxygen you use during physical activity; and body composition analyses, which estimate or measure the amount of body fat, muscle, and bone in a person's body.

Another option is something called the doubly labeled water (DLW) method (almost exclusively used in research or clinical settings), which Dunston defines as another method to measure metabolism. "Here, burned calories are measured by tracking the amount of carbon dioxide that a person exhales throughout their daily activities," Dunston tells mindbodygreen. "During the test, your blood is drawn at various intervals during exercise and the levels are compared. When your body doesn't have enough oxygen to promote the conversion of calories into energy, it switches to anaerobic respiration, which produces lactic acid or lactate. This is only done in a medical setting under specific conditions," she explains.

If you come to find that your metabolism is slowing down, the great news is that our metabolism and metabolic health are flexible, with several factors under our control. Here are key lifestyle habits you can incorporate into your daily routine in order to help speed up your metabolism.

If you tend to stick to the same meals and snacks from day to day, it's time to switch up your daily menu. According to Vickery, eating a diverse diet "will ensure that you are getting the nutrients you need in order for your body to function and perform at its best." 

Vickery warns that a lack of sleep "can impact hormones that control appetite and metabolism, so getting enough sleep may help [speed things up]." If you're having trouble falling asleep or staying asleep through the night, it might be worth chatting with a sleep specialist to explore ways to improve your snooze.

In a 2016 review published in the journal Frontiers in Nutrition, researchers found that drinking water promotes water-induced thermogenesis2 (a process in which water has a thermic effect over the food you eat and therefore breaks down as energy) and increases metabolic rate by up to 30% for an hour in animal studies. By now, you probably know that staying hydrated helps you perform at your best, but according to these findings (and Vickery), it can also help your metabolism perform at its best.

According to Dunston, physical activity can help give your metabolism a boost. Weight training, she says, is especially beneficial.

"Increasing your muscle mass helps you to burn calories at a higher rate when you're sitting and doing nothing. This is because your muscles are the biggest utilizer of your caloric intake; they are hungry for energy," Dunston says. "You burn calories just sitting and breathing while doing nothing, so if you can increase your muscle mass with resistance training or weights, then you will burn more calories while sitting and doing nothing."

In addition to the aforementioned tips, targeted botanicals can also help flex your metabolism potential. By incorporating a supplement like mindbodygreen's metabolism+ into your daily routine, you can benefit from clinically researched plant bioactives.

The formula is vegetarian and free of gluten, GMOs, dairy, and soy, and void of all major food allergens. Highlighted ingredients include veld grape (which is rich in flavonoids, stilbene, and ketosterone bioactives that combat oxidative stress, promote healthy blood pressure and fasting blood sugar, and support a healthy weight) and grains of paradise (an edible spice from the ginger family that helps to burn calories by activating thermogenic brown adipose tissue3, aka BAT).* The supplement also delivers cayenne pepper, which is rich in antioxidants and helps curb cravings4, as well as antioxidant-rich EGCG and caffeine sourced from green tea leaves that encourage metabolic synergy5 when combined.*

It's natural for your metabolism to fluctuate throughout your life. It's fast when you're young and gradually slows down with age—but not as rapidly as you might think. New findings suggest that your metabolism stays somewhat consistent between 20 and 60 years old (obviously, personal differences and clinical scenarios can differ!), but it can slow down significantly due to muscle losses, hormonal or energetic fluctuations, nutrient deficiency, or a higher burden of toxin exposure. 

Luckily, there are ways to invigorate and reset your metabolism naturally—such as making changes to your diet, getting better sleep, and taking a targeted supplement like mindbodygreen's metabolism+.* If you feel as if your metabolism might be slowing down, talk to your health care provider for further assessment.