7 Sneaky Signs Your Metabolism Is Slowing Down, According to a Doctor and Dietitian

Having a fast metabolism is critical to maintaining optimal health, especially as you get older. That said, you only have so much control over your metabolic rate, which is why it’s important to be able to recognize the signs your metabolism is slowing down so you can take steps in your everyday life to keep it running as speedily as possible.

“To put it simply, a faster metabolism means that at rest, your body is using more energy (measured in calories) for normal body functions like breathing, heartbeat, and brain activity,” explains Courtney Pelitera, M.S., R.D.N., C.N.S.C., a registered dietitian nutritionist at VNutrition. “Therefore, you use more calories just to function properly throughout the day than someone with a slower metabolism.”

Meet the experts: Courtney Pelitera, M.S., R.D.N., C.N.S.C., a registered dietitian nutritionist at VNutrition; Brooke Bussard, M.D., a lifestyle medicine health coach.

Here, experts explain some of the reasons your metabolism might start to slow down, plus how to tell if this is the case and what you can do about it.

There are three main reasons metabolism can slow down, says Brooke Bussard, M.D., a lifestyle medicine health coach. The first is muscle loss. “Muscle tissue is metabolically active, meaning it burns more calories than fat,” Dr. Bussard explains. “As we lose muscle, our overall energy needs decrease.” This is the primary reason that metabolism tends to slow down as you age, Pelitera adds. According to the Cleveland Clinic, you gradually begin losing muscle mass in your 30s, a process that speeds up once you hit your 60s. All told, you may lose as much as 8% of your muscle mass per decade, which can have a major impact on your metabolism if you’re not taking steps to combat it.

“As we age, hormones such as testosterone and estrogen decrease, leading to a decrease in muscle mass,” says Pelitera. Levels of these key hormones drop drastically during menopause, which is why muscle loss tends to speed up (and metabolism tends to slow down) in women after they complete the menopausal transition, per research in Frontiers in Endocrinology.

The next reason your metabolism might be slowing down is an underlying health condition, Dr. Bussard says. “Conditions like hypothyroidism or poorly controlled diabetes can decrease how efficiently the body uses energy,” she explains. These fall into a group of conditions known as metabolic disorders, or illnesses in which your body struggles to process carbohydrates and fats effectively, leading to issues like insulin resistance, obesity, or high blood pressure, according to research in Diabetes, Metabolic Syndrome and Obesity.

The final factor, says Dr. Bussard, is chronic undereating. “Consistently eating too little can lead the body to adapt by becoming more energy-efficient, reducing overall calorie expenditure over time,” she explains.

So, how can you tell if your metabolism is slowing down? There are a couple key signs. “A major sign would be weight gain without changing any diet or lifestyle habits,” says Pelitera. “A metabolism that is slowing down will require less energy.” So if you’re taking in more energy than your body requires, the rest of it will be stored as fat.

Dr. Bussard says that changes in your body composition, such as losing muscle and gaining fat (even if the number on the scale isn’t changing much) can also signal that your metabolism isn’t as speedy as it once was.

“Fatigue is another common sign,” adds Dr. Bussard. “While this can relate to overall calorie intake, it’s often influenced by micronutrient intake as well. Vitamins and minerals play essential roles in the chemical reactions that drive energy production in the body.”

While weight gain, changes in body composition, and fatigue are the most common signs, there are a few other additional changes you might experience. Pelitera says that these include feeling sluggish, feeling cold all the time, mood fluctuations, and changes in your appetite.

“Metabolism is not something that we are in control of. Our hormones are going to decrease with age, naturally,” Pelitera says. However, there are steps you can take to slow down these changes, especially as they relate to muscle loss. “Because muscle plays a key role in energy expenditure, maintaining it is essential,” says Dr. Bussard. “Incorporating activities that challenge your muscles can help preserve metabolic health.” That means starting a strength-training regimen or incorporating more of the best strength-training exercises into your weekly workout routine. The Centers for Disease Control and Prevention (CDC) recommends strength training at least two days per week, making sure to work all the major muscle groups.

“Nutrition also plays an important role,” Dr. Bussard says, of the importance of filling your plate with metabolism-boosting foods. “Focusing on nutrient-dense whole foods like fruits, vegetables, legumes, and whole grains provides the vitamins and minerals your body needs to support energy production at the cellular level.” Pelitera adds that eating consistently throughout the day, drinking enough water, and getting sufficient sleep also contribute to a healthy metabolism.