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These habits might seem healthy, but on closer look, they aren’t doing your metabolism any favors.

Reviewed by Dietitian Lisa Valente, M.S., RD

Key Points

• Many things can impact metabolism, but after 40, certain habits may harm more than help.
• Cutting calories and carbs, only doing cardio and intermittent fasting can slow metabolism.
• Support your metabolism with protein, sleep, stress management and movement.

Anyone near or past the age of 40 can tell you that your body changes with age. Hormonal, metabolic and lifestyle shifts can change body composition and health. A glance in the mirror or abnormal bloodwork may prompt you to adopt healthier habits, but some seemingly “healthy” habits may do more harm than good for your metabolism.

Your metabolism encompasses the chemical reactions in the body that convert food into energy. When people wonder if their metabolism is slow, they’re typically referring to their metabolic rate or daily energy expenditure, or how many calories the body burns throughout the day. Your metabolism stays fairly stable between the ages of 20 and 60, and then starts to decline. However, muscle loss begins in our 30s, and metabolic rate is largely driven by the amount of muscle someone has., “As we age, we tend to lose lean body mass, which is about 50 percent skeletal muscle, and when we gain weight, it tends to be fat,” says Elizabeth Ward, M.S., RDN. “The more muscle you have on board as you age, the higher your metabolic rate.”

It’s natural to lose muscle with age, but if you want to keep your metabolic rate high, a main goal should be preserving muscle. Some habits that seem healthy accelerate muscle loss. Here are the “healthy” habits dietitians say may actually slow your metabolism after 40.

1. Eating Low-Calorie Meals and Snacks

“If you’re gaining weight after 40, it makes sense to think that cutting way back on calories at meals and snacks would be helpful,” says Ward. “However, this can lead to under-eating that can make it difficult or impossible for your body to make new skeletal muscle cells because you aren’t eating enough protein and carbohydrate.” Not only that, rapid weight loss means more muscle loss. Muscle burns more calories than fat tissue, so we want to keep as much muscle as possible on board, Ward says.

Eating low-calorie meals can also increase hunger, so while eating fewer calories seems better, it can backfire. Shift your focus from trying to eat less to trying to eat more of the foods that fuel your metabolism. “Focus on a balanced eating plan with adequate energy from carbohydrate and enough protein that’s slightly lower in calories than what you typically eat if weight loss is the goal,” says Ward. Colorful fruits and vegetables paired with lean proteins and whole grains support a healthy metabolism.

2. Only Doing Cardio Workouts

“Cardio workouts are good for your heart health and they can burn a lot of calories to help with weight control,” says Ward. But only doing cardio workouts like running or biking could slow your metabolism. That’s because cardio exercise does little to build and preserve skeletal muscle tissue, which over time, may lower your calorie-burning capacity, says Ward.

Skipping strength training can lead to even more muscle loss than what naturally happens in your 30s. This doesn’t mean you should neglect cardio altogether. It’s about balance. “The best exercise regimen includes cardio and resistance training,” Ward says. “You can cut back on cardio and add at least two sessions of strength training weekly (about 20-30 minutes each), or you can add the strength training to your cardio.”

3. Cutting Carbs

It’s popular to cut carbs to help with weight gain or insulin resistance, two issues that can show up in your 40s. And while reducing carbohydrates can certainly aid weight loss and improve blood sugar control, cutting out all carbs could be detrimental to your metabolism. When you cut carbs, you naturally eat fewer calories, which can lead to weight loss. That might be your goal, but when you lose weight, your resting metabolic rate goes down. Not only that, you lose muscle alongside fat if you aren’t doing anything to preserve the muscle. You can combat some muscle loss by lifting weights and eating adequate protein, but you’ll get the most out of your workouts if you replenish with carbs and protein.,

“Cutting out all carbohydrates means that you are also limiting important nutrients found in carbohydrates like dietary fiber and key micronutrients like B vitamins, magnesium, zinc, iron and important phytochemicals that can play a huge role in disease prevention,” says Renee Korczak PhD, RDN, CSSD. Skip the refined carbs, and aim for whole grains, fruits, vegetables and legumes, which provide fiber to support blood sugar control and a healthy metabolism.

4. Intermittent Fasting

Intermittent fasting involves eating within a certain time window, usually 8-10 hours. It doesn’t directly slow metabolism and may even improve metabolic health by reducing inflammation and improving glucose metabolism. But, if not done thoughtfully, intermittent fasting could slow your metabolism. “For women in perimenopause (and menopause), a shortened eating window makes it more challenging to consume enough protein to preserve lean muscle mass, which is essential for healthy aging and metabolic health,” says Jaime Shelbert, RDN, LDN.

“Meal timing also matters as research points to aligning food intake with the body’s natural circadian rhythm to support metabolic health,” says Shelbert. When intermittent fasting, people often start eating in the middle of the day, essentially skipping breakfast. This can push meals later into the evening, which impairs glucose metabolism and increases the risk of metabolic disorders. “If you choose to practice intermittent fasting, focus on adequate protein, strength training and an earlier eating window, plus consider whether it is a sustainable approach that fits your lifestyle,” says Shelbert.

Other Tips for Metabolism After 40

To support a healthy metabolism after 40, experts say skip the trendy diets and focus on these habits.

• Prioritize protein: Protein supports muscle growth, and high-protein diets are associated with greater daily energy burn. The body also burns more calories digesting protein compared to carbs and fat. Aim to have protein at each meal and snack, preferably from whole foods, like Greek yogurt, cottage cheese, eggs, beans, lentils, lean meat, poultry and fish, says Korczak.

• Don’t slack on sleep: Lack of sleep and poor-quality sleep negatively impact how carbohydrates and fats are metabolized. This can lead to insulin resistance, obesity and heart disease. Aim for 7-9 hours of good quality sleep each night.

• Take stress seriously: Stress spikes the hormone cortisol and chronically elevated cortisol drives the storage of belly fat and can lead to obesity. Take stress as seriously as you take your diet and exercise. Build in time to journal, meditate, walk or do yoga.

• Move more: Get more movement throughout the day outside of scheduled workouts. This increases what’s called NEAT, non-exercise activity thermogenesis. Think movements like walking, fidgeting or doing chores. Low levels of NEAT are associated with obesity and type 2 diabetes, so schedule that walk break and take the stairs.,

Our Expert Take

Maintaining a healthy metabolism after the age of 40 comes down to preserving muscle and eating a balanced diet with adequate protein, carbohydrates, healthy fats and vitamins and minerals. While metabolism remains fairly stable until the age of 60, muscle loss begins much earlier, so strength training and prioritizing protein are of utmost importance. Don’t forget about stress and sleep too, which both impact hormones and metabolism.