Understanding Your Metabolism — What It Is, What It Does, and How It Works

Calvin Wu, MD
December 8, 2021
4.5 mins

Common knowledge says that our metabolism is this mysterious thing we’re all born with that predetermines how fast we burn calories and, hence, how hard or easy it is for us to lose or gain weight — and that if you can somehow “speed up your metabolism,” you’ll be able to eat more while still maintaining your target weight, right?

Well, not exactly. Your metabolism is far more complex than that. 

It’s true that metabolism is linked to weight, but in fact a slower metabolism is rarely the cause of excess or unwanted weight. In this post, we’ll explain what metabolism really is and debunk some common misconceptions. 

What Is Metabolism?

The word “metabolism” refers to the chemical processes that occur within the body when it is converting food into energy (which is measured in calories). This energy is then used to support our physical activity and to sustain basic bodily functions, including:  

     • Breathing

     • Delivering nutrients to your cells 

     • Digesting food

     • Eliminating waste from your body 

     • Powering muscles

Metabolism is broken down into two main processes:

     • Anabolism — the storing of new energy, supporting new cells, and maintaining body tissues 

     • Catabolism — the breaking down of energy to move and use your body

The rate at which you burn calories (or energy) is called your metabolic rate. This is what most people think of when referring to metabolism. Your metabolic rate includes two important numbers:

     • Basal metabolic rate (BMR) — the number of calories needed to support essential functions, like breathing and circulating blood

     • Calories burned during physical activity — including walking, doing chores, and exercising 

What Are Common Misconceptions Surrounding Metabolism?

“Metabolism” has become a buzzword, especially when it comes to weight management. It’s a common belief that some people are born with a “good” metabolism, or that if you can just speed up your metabolism, weight loss will come more quickly. And although there are small elements of truth to these statements, they do not accurately define what a metabolism is or how it works.

Many variables affect what a “good” metabolic rate is for an individual person — and your metabolism can change from hour to hour, as things like exercise have an immediate effect. (However, in terms of your overall health, you should take a longer-term view.) Have a conversation with your healthcare provider about the best ways to keep your metabolism in a good place.

Here are some of the most common misconceptions about metabolism:

Myth: Your metabolism is fixed. 

Fact: Your metabolism can be changed and affected by many factors, including:

     • Activity level

     • Body size

     • Body temperature

     • Food intake

     • Hormones

     • Muscle mass

Myth: A person with less body fat has a faster metabolism than a person with more body fat. 

Fact: Although it may sound counterintuitive, a person with less body fat doesn’t always have a faster metabolism than a person with more body fat. 

In general, the larger a body is, the more energy it takes to support basic functions and movement. For example, if two are people doing the exact same exercise, the one that has more body mass will likely burn more calories — so their metabolic rate would be described as faster.

Myth: Your metabolism gets worse as you age. 

Fact: Aging has little impact on metabolism until much later in life, and even then, the impact is minimal. 

Whether they were in their 20s, 30s, 40s or 50s, we’ve all likely heard someone say that their metabolism is slowing down because of their age. But that’s probably not truly the case. Outside of our first year of life, when our growth is exponential, our daily calorie needs don’t start to change until we’re in our 60s — and even then the change is minimal. 

Myth: Eating breakfast jump-starts your metabolism. 

Fact: Breakfast — the most important meal of the day — may not actually be that influential on your metabolism. 

For a long time, breakfast has been touted as a key part of a healthy morning and a properly functioning metabolism. And although some research shows that people who eat breakfast are less likely to be obese, there’s not nearly as much evidence that shows breakfast to be a direct cause of this. When it comes down to it, your metabolism is much more affected by the total amount of food you eat throughout the day than by when you consume those calories. 

Myth: Supplements can boost your metabolism. 

Fact: Although supplements can have a small impact on metabolism, they’re unlikely to make a significant difference.  

When it comes to your metabolism, there is no magic pill you can take that outweighs diet and lifestyle changes. There are many supplements that advertise the ability to “jump-start” your metabolism and help you “shed weight fast,” but many of these products are marketed with false promises and a lack of evidence to support the manufacturer’s claims. 

How Can I Improve My Metabolism?

If you’re looking to improve your metabolism, here are some things you can do:

     • Eat more protein — The TEF (thermic effect of food) refers to the increase in your metabolism after eating. Protein causes the highest rise in TEF. 

     • Exercise regularly — Exercising increases the amount of calories you burn, which improves your metabolism. 

     • Increase daily activity — If you are unable to set aside dedicated time for exercising, increasing your amount of daily physical activity (by doing things such as short walks, cleaning, or even getting out of your office chair) can help. 

     • Gain muscle — Muscle requires calories to function. Strength-training exercises that increase muscle mass can help improve your metabolism. 

     • Get more sleep — Poor sleep can have a negative impact on your metabolism and has also been linked to increased blood sugar levels.

     • Monitor calorie intake — Although you don’t have to count every single calorie you consume, making sure you’re within the necessary caloric range for your body helps keep your metabolism working efficiently. Eating too many or too few calories can have a negative impact on your metabolism. 

With any change to your diet and lifestyle, it’s wise to discuss your health goals with your primary care provider, to see if the change will move you toward those goals. At Carbon Health, our providers are standing by to help you make informed decisions about your health. 

Carbon Health’s medical content is reviewed and approved by healthcare professionals before it is published, but it is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Talk to your healthcare provider about questions you may have regarding your health or a medical condition, and before making changes to your healthcare routine.


Calvin Wu, MD

Calvin Wu, MD, graduated from the Keck School of Medicine of USC and specialized in endocrinology at Harbor-UCLA Medical Center. He is the director of the Virtual Diabetes Program at Carbon Health.

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