When people struggle with weight loss, the first suspect is often their metabolism. It’s a familiar frustration when you wonder why a friend can eat twice as much and never gain weight, while you seem to add kilos just by looking at dessert. In fact, entire industries have been built around this frustration. Globally, metabolism-related pills and diet products are worth over 33 billion in the U.S. alone, selling pills, powders, and shortcuts that promise to “rev up” metabolism. 

But metabolism isn’t a mystery switch you can turn on with a pill or supplement, it’s a complex process our body relies on every moment of the day. And while some factors like age or genetics are outside of your control, there are practical, evidence-backed ways to support a healthy metabolism. 

Understanding What Metabolism Really Is 

Metabolism is the sum of all the chemical reactions in the body that keep you alive. It powers everything from breathing to digestion.  

When people talk about metabolism in the context of weight, they are usually referring to basal metabolic rate (BMR), the calories your body burns at rest to keep you alive. How high or low your BMR is depends largely on how much muscle and fat you carry. Muscle burns more calories than fat, even when you’re not moving. That’s why two people of the same weight can have very different metabolic rates depending on body composition. 

Age, gender, weight history, and lifestyle also play a role. Metabolism naturally slows as you get older, and repeated cycles of dieting can also make it less efficient. 

Why Age Slows Metabolism and There’s Another Overlooked Reason Why Metabolism Slows: dieting itself 

By the time most people reach their 40s, their bodies are already experiencing a gradual decline in muscle mass. Research shows that muscle loss accelerates with each passing decade, while body fat tends to increase. Since muscle tissue is more metabolically active than fat, losing muscle means burning fewer calories, even at rest. This explains why weight gain feels inevitable with age, even when diet and activity levels stay the same. 

Another hidden reason metabolism slows is repeated dieting. When people lose a large amount of weight, they lose both fat and muscle too. That loss of muscle lowers calorie-burning capacity. 

What’s more troubling is that metabolism often doesn’t return to its previous level, even if the weight comes back. Research has shown that with every round of dieting, calorie burn slows further by up to 15% in ways that can’t simply be explained by body size changes. 

This is why “yo-yo dieting” feels harder each time. The body becomes more resistant to burning energy, making weight loss increasingly difficult. 

Ways to Support a Healthy Metabolism 

What to Avoid. Despite flashy promises, diet pills and supplements don’t offer lasting results. Ingredients like caffeine or capsaicin (found in chili peppers) may cause a short-term boost in calorie burn, but the effect fades quickly.

Two major reviews covering more than 120 studies  found no reliable long-term results. What they did find was clever marketing.  Supplements won’t give you a faster metabolism; but investing in consistent habits (movement, balanced eating, and sleep) pays off far more. 

Rethink What’s on Your Plate. The body uses energy to digest, absorb, and metabolize food. This is known as the thermic effect of food (TEF), and it accounts for about 10% of daily calorie use. The effect is greatest with protein, since it requires more energy to break down.

Proteins have the highest thermic effect. The body burns roughly 15% of protein calories during digestion, compared to around 10% for carbohydrates and less than 5% for fats. That’s why including protein in meals can slightly raise your metabolic rate while also helping you feel full longer. 

That doesn’t mean you should switch to a protein-only diet. A balanced plate of protein, vegetables, whole grains, and healthy fats is what sustains energy, supports long-term health, metabolism, and prevents disease. 

Move Your Body and Build Muscle. Exercise is one of the most reliable ways to improve metabolism because it builds muscle mass. The more muscle you have, the higher your  metabolic rate. Even when you’re not moving, muscle burns more calories than fat.

Experts recommend at least 30 minutes of daily activity, paired with two sessions of strength or resistance training each week. Varying your routine also matters,  mixing it up prevents boredom and keeps motivation alive. But repeating the same exercise day after day can lead to boredom and drop-off.  

Protect Your Sleep. It’s easy to overlook, but poor sleep can derail metabolism just as much as inactivity or poor diet. Sleep deprivation disrupts appetite-regulating hormones, increasing hunger and cravings, particularly for high-sugar and high-fat foods.

Lack of rest also interferes with how the body processes glucose, reduces energy expenditure, and encourages fat storage. Studies consistently link short sleep duration to higher risk of weight gain and metabolic dysfunction. 

Seven hours of quality sleep is a good benchmark. A simple way to achieve this is creating a bedtime buffer; no screens for at least one hour before bed. Blue light from devices suppresses melatonin, the hormone that signals it’s time to sleep.