Your metabolism is the way your body uses energy. Your body needs energy to breathe, pump blood, digest food, and move. It keeps working even while you sleep.

Many people blame a slow metabolism when they gain weight. But weight gain is more complex than that. Your food, activity, sleep, muscle mass, medicines, and health conditions can all play a role.

Some daily habits can also make weight management harder. Eating too little, sitting all day, sleeping poorly, and skipping strength training are a few examples.

Here are six common mistakes that may work against your metabolism and your long-term health.

1. Eating Too Few Calories

Eating fewer calories can help with weight loss. But eating far too little can work against you.

When you lose weight, your body needs less energy than it did before. Your body can also adapt to a lower calorie intake by using less energy. This can make further weight loss harder.

Very low-calorie diets can cause large drops in energy use. In one study, people who ate about 890 calories a day had their total daily energy use fall by about 633 calories per day after three months.

That does not mean you should stop eating less to lose weight. It means extreme diets are not a good long-term plan.

A better approach is a modest calorie deficit with enough protein, nutrients, and food to support your body. If you need to lose a large amount of weight, a doctor or dietitian can help you choose a safe plan.

2. Eating Too Little Protein

Protein does more than help you feel full. It also helps your body build and maintain muscle.

Your body uses more energy to digest protein than it does to digest carbohydrates or fat. This is called the thermic effect of food. Protein has the highest thermic effect of the three.

Protein also matters when you are losing weight. Without enough protein and activity, some of the weight you lose can come from muscle. Losing muscle can lower the amount of energy your body uses at rest.

Research has found that higher protein intake may help reduce this drop in energy use during weight loss. One study found that about 1.2 grams of protein per kilogram of body weight per day helped prevent a larger decline in energy expenditure.

Your exact protein needs can vary. Your age, body size, activity level, and health all matter. The goal is not to eat as much protein as possible. It is to get enough as part of a balanced diet.

3. Sitting Too Much and Moving Too Little

You can exercise for 30 minutes and still spend most of your day sitting. Work, driving, meals, television, and phone use can add up to many hours in a chair.

This means you may burn very little energy outside your workout.

One term for this is NEAT, which stands for non-exercise activity thermogenesis. It means the energy your body uses for everyday movement that is not formal exercise.

Walking around your home counts. So does cleaning, taking the stairs, standing while talking on the phone, or walking during a break.

You do not need a gym to move more. Get up from your desk every hour. Walk while taking a phone call. Take the stairs when you can. Small amounts of movement can add up across the day.

4. Treating Sleep as Optional

Sleep is not wasted time. Your body needs it to work well.

Regularly getting too little sleep can affect appetite, weight, blood sugar, and other parts of metabolic health. The CDC reported that 30.5% of U.S. adults slept fewer than seven hours per night in 2024.

Research also shows that short-term sleep loss can affect energy use. In one study, healthy adults who slept only four hours a night for five nights had an average 2.6% drop in resting metabolic rate. Their rate returned to normal after 12 hours of uninterrupted sleep.

When you sleep can matter, too. Sleeping during the day and staying awake at night can disrupt your body’s internal clock.

Try to keep the same sleep and wake times each day. Give yourself enough time to sleep. Keep your bedroom dark and quiet. Limit bright screens before bed.

If you often struggle to sleep or feel tired even after sleeping, talk with your doctor. Persistent sleep problems may need medical attention.

5. Drinking Sugary Beverages Every Day

A soda or sweetened coffee may not seem like much. But drinking them every day can add a lot of sugar and calories to your diet. Unlike solid food, drinks may not make you feel as full.

Regular intake of sugary drinks is linked with weight gain, insulin resistance, and a higher risk of Type 2 diabetes. These drinks are not proven to directly “slow” metabolism in every person, though. Research on that specific effect is mixed.

The bigger concern is what happens when sugary drinks become a daily habit. They can make it easier to take in more calories than your body needs.

Try water, sparkling water, or unsweetened tea instead. If you add sugar to coffee or tea, slowly use less. You do not have to change everything in one day.

6. Skipping Strength Training

Muscle needs energy to maintain itself. This is one reason muscle mass matters when you are trying to manage your weight.

You can lose some muscle when you lose weight. Muscle mass can also decline as you get older. Less muscle means your body may use less energy at rest.

Strength training can help protect and build muscle. You do not need to lift heavy weights to start. Resistance bands, bodyweight exercises, and weights can all be useful.

One six-month study found that people who did about 11 minutes of strength training three days a week had a 7.4% increase in resting metabolic rate on average. They also burned about 125 more calories per day. This was one study, so the results will not be the same for everyone.

The goal is not to make your metabolism “fast.” It is to keep your muscles strong and support healthy movement as you age.

When a Slow Metabolism May Be Something Else

Sometimes weight gain has little to do with metabolism alone. Your sleep, diet, activity, genes, medicines, and overall health can all affect your weight.

Some medical conditions can also play a role. Hypothyroidism, for example, can cause weight gain, tiredness, feeling cold, and other symptoms. Polycystic ovary syndrome, or PCOS, can also make weight management harder for some people.

Some medicines may contribute to weight gain as well. Your doctor can review your medicines, health history, sleep, eating habits, and activity level to look for possible causes.

If your weight changes without a clear reason or keeps increasing despite consistent changes, do not assume you simply have a “slow metabolism.” Talk with your doctor. Finding the cause is more useful than guessing.

Conclusion: Stop Chasing a Faster Metabolism

Your metabolism is not controlled by one food, drink, or exercise. It is shaped by many things, including your muscle mass, activity, sleep, diet, age, medicines, and health.

There is no magic supplement that suddenly makes your body burn more calories. Extreme diets are not the answer either.

Focus on habits you can keep. Eat well, get enough protein, move every day, train your muscles, and protect your sleep.

The goal is not to have the fastest metabolism possible. The goal is to keep your metabolism healthy and support your body for the long term.