How Metabolism (Really) Works & 4 Ways to Max It Out

We’ve decoded the mystery of what metabolism is so you can boost its efficiency.

Published November 17, 2022
Woman drinking water after workout

If you're like many of us, you blame your metabolism any time you experience an unintended weight loss or weight gain. If the numbers on the scale don't quite cooperate, you start thinking about ways to change your metabolism to get your body back to where you want it to be. But the concept of metabolism can be confusing, especially where weight loss is concerned. Can you really change your metabolism? And what is metabolism anyway?

Understanding the definition of metabolism and the way that it works can help shed some light on why you might see changes in your weight. Once you have a handle on all the factors that affect your metabolism, you can take steps to reach your weight loss, weight gain, or weight maintenance goals.

What Is Metabolism?

Metabolism isn't necessarily a single thing in your body, like a muscle or an organ. The term "metabolism" refers to a complex process that includes all the steps involved in turning the food you eat into energy. Metabolism also includes the processes involved when your body uses that energy to carry out a wide range of functions, like breathing or muscular movement.

Metabolism involves two main parts: catabolism and anabolism. Eating triggers a process that breaks down your food into smaller pieces (catabolism). Your stomach and intestines absorb these tiny pieces and release energy. Then, your body uses that fuel to build cells and tissues (anabolism) and to keep your body's important operations, like breathing and digesting food, running like a well-oiled machine.

Metabolism Infographic

According to Medline, metabolism provides energy for basic bodily functions, even at rest. These functions include:

  • Blood circulation

  • Body temperature management
  • Breathing
  • Contracting muscles
  • Digesting food and nutrients
  • Functioning of the brain and nerves
  • Waste elimination through urine and feces

Everything your body does (even when you're sitting still or sleeping) requires energy, and your metabolism is only too happy to provide what you need.

How to Get a Healthy Metabolism

Many people believe that the key to reaching and maintaining a healthy weight is having a healthy metabolism. But what does that mean, exactly? Is it better to have a fast metabolism? And if you believe that you have a slow metabolism, should you do something to jumpstart it?

In casual conversations, people often use the term "metabolism" to refer to their metabolic rate, or the rate at which your body uses energy to carry out daily functions. Learning about metabolic rate can help you to understand how weight loss works and how metabolism plays a role.

Understand Basal Metabolic Rate

Basal metabolic rate (BMR) is the number of calories needed to sustain metabolic processes when your body is at rest. BMR is also sometimes called resting metabolic rate (RMR). Your basal metabolic rate is a way to measure how fast you burn through energy or calories when your body is at total rest.

The genes you are born with help to establish your BMR. Other factors that influence BMR include weight, height, age, and gender. Since these are not factors that you can generally change, your basal metabolic rate is not something that you can easily modify, although your BMR is likely to change throughout your life. Studies suggest that BMR starts to decline around age 60.

So is a fast BMR better than a slow one if your goal is weight loss or weight maintenance? Harvard Medical School (HMS) explains that while many people associate a high metabolic rate with staying thin, this is not strictly true.

Rush University Medical Center (RUMC) reports that if you have a fast basal metabolic rate, you burn calories more quickly than someone with a slow BMR. But remember, BMR refers to the calories you burn when your body is at rest. BMR only accounts for about 50%-70% of the total number of calories that you burn throughout the day. The other 30%-50% is determined by factors that you can modify.

Focus on Total Daily Energy Expenditure

Even though there is not always a lot you can do about your basal metabolic rate, there is another number that is important when considering the health of your metabolism - your total daily energy expenditure or TDEE. This is the total number of calories you burn throughout the day or your total metabolic rate. If you want to lose or gain weight, total daily energy expenditure is the number you need to focus on.

Your TDEE is dependent on a wide variety of factors, many of which are in your control.

Physical Activity

Any physical movement helps to increase the number of calories that your body needs to function. Physical activity generally accounts for approximately 20% to 30% of your TDEE, although the number can vary depend on how active you are. There are two different types of movement that contribute to this number:

  • Exercise includes all the movement you participate in that raises your heart rate, strengthens your muscles, and gets your blood pumping.
  • Non-exercise movement is all the activity you participate in that is not exercise. When you burn calories from non-exercise movement it is referred to as non-exercise activity thermogenesis or NEAT. Calories burned walking up the stairs, folding your laundry, carrying groceries into your house, all play a significant role in the total number of calories you burn throughout the day. In fact, for many people NEAT contributes more to your TDEE than calories burned during exercise.


Different foods cause different metabolic reactions. The digestion of protein, for example, may increase your metabolism more than the digestion of fats and carbohydrates. The calories burned from digestive processes is called the thermic effect of food or TEF. But while you might be tempted to eat more protein to boost your TEF, keep in mind that TEF only accounts for about 10% to 15% of your TDEE. So the extra calories you burn by eating a serving of protein rather than a serving of carbs will be minimal.

The timing of your diet might also play a role in the total number of calories that you burn during the day. At least one study has suggested that intermittent fasting (going for many hours without eating) might lower your resting metabolic rate slightly. The study was small in scope and the change in resting metabolic rate only amounted to about 100 calories, so more studies will need to be conducted to understand this potential effect.

4 Tips to Boost Your Metabolism

There isn't much you can do about several factors that impact metabolism - like your age. But you can make the most of other factors to keep your metabolic machine humming along.

Eat a Healthy Diet

Let's dig a little deeper into diet. What you eat is important. Good nutrition not only helps you to burn more calories through the thermic effect of food, but good nutrition also helps you to stay active so that you can burn more calories from movement.

RUMC suggests choosing "whole grains, lean proteins, vegetables, and fruit, which your body can more readily use to fuel its functions and activities."

  • Carbohydrates: Build energy-boosting meals around healthy whole grains and nutrient-rich fruits and vegetables.
  • Fat: If you eat fat, try to stick to "good fats" like fatty fish, vegetable oils, nuts, and seeds.
  • Protein: Protein helps your body to build muscle when combined with strength training. Choose lean proteins like eggs, beans, and lentils and try to limit fatty meats.
  • Water: Stay hydrated by drinking plenty of water (eight 8-ounce glasses per day) to prevent fatigue.

Some claim caffeine and spicy food will increase your metabolism, but the medical community is divided on suggesting these dietary choices because of the risk of overconsumption and possible harm. Be wary of products that claim they increase your metabolism. Studies are lacking in this area and the Food and Drug Administration (FDA) does not regulate supplements the same way they do medications.

Increase Physical Activity

Exercise kicks metabolism into high gear. When you get your heart pumping and muscles straining, your energy needs increase, so your metabolic rate has to pop into high gear to keep up with all that energy use. The type of exercise you do has an impact on how much your metabolism increases.

HMS suggests incorporating high-intensity sessions into your workouts. High intensity exercise involves short bursts of very strenuous work, followed by brief segments of active rest. This type of training helps you to burn more calories in a shorter period (as compared to moderate or low intensity exercise). Experts also advise that weight training workouts can help to improve metabolism.

But remember that exercise only increases metabolism temporarily, so it is important to continue to keep moving throughout the day. Try any of these methods to boost your daily NEAT:

  • Take the stairs instead of the elevator whenever possible.
  • Set a timer or use an activity tracker to prompt 5 minute walking breaks each hour
  • Make a commitment to take a short walk after dinner each day
  • Stand up and stretch during commercial breaks when watching TV
  • Get a standing desk for your workplace so that you can stand and move during the workday

Get Adequate Rest

Exercise and non-exercise movement are essential for a healthy metabolism, but getting adequate rest is important as well. If you're exhausted when you wake up in the morning, it is going to be harder for you to stay active throughout the day and studies even suggest that you make less healthy food choices when you are tired.

So if weight loss is your reason for changing your metabolism, sleeping better can help you reach your goal. According to a research report in the journal Obesity, better sleep quality and sleeping at least 7 hours per night might increase the likelihood of weight loss success by as much as 33%.

Maintain Good Overall Health

Sometimes your metabolism starts acting funky because of a health condition. Diabetes, for example, can affect metabolism because of its impact on the hormone insulin. In addition to diabetes, these other conditions can also negatively affect your metabolism, according to RUMC:

Many of these can conditions be treated with medications. So, if you experience any sudden changes in weight and energy levels and you are concerned that a metabolism disorder might be involved, speak with your healthcare provider.

Why Metabolism Matters

Metabolism keeps your body up and running. You can compare metabolism to the way your car runs on gasoline: you put fuel into your car, and it uses that fuel to create energy that allows your engine to start, air conditioning to work, and music to blast.

In the same way, metabolism uses the food you eat to create energy to walk, talk, sing, dance, work, and play. And metabolism allows us to breathe! The fuel you put in to your body affects the way your "car" runs - so remember to choose healthy food, exercise regularly, and get quality rest. These things will help keep your metabolism purring along.

How Metabolism (Really) Works & 4 Ways to Max It Out