The Truth About Metabolism

WASHINGTON — Metabolism is a common buzzword used to sell products and convey different theories. Many popular myths and questions surround this process. Are certain foods good or bad for your metabolism? Do some people have a slower or faster metabolism than others?

Here, we’ll use the latest scientific research to try to demystify metabolism as much as possible. We’ll explain how metabolism works by defining key terms and addressing these popular myths and questions.

How Does Metabolism Work?

It is no secret that the popularity of metabolism goes hand in hand with attempting to understand weight loss and gain. Theoretically, consuming fewer calories than you burn should cause weight loss, and consuming more calories than you burn should cause weight gain.

However, the formula doesn’t always work, and if you have ever struggled with weight loss or gain, you may have heard your metabolism could be to blame. 

Defining Metabolism and Key Terms

The word “metabolism” refers to multiple chemical processes in your cells that convert calories and oxygen to energy. Your body uses this energy for many functions, including breathing, blood flow, temperature regulation, heart, brain and other organ activity. Fifty to 70% of your energy goes toward fueling these processes.

When you hear about “burning calories,” almost 70% of the calories you consume go toward fueling these functions. The remainder of the calories that you “metabolize” are used for energy to digest food and for physical activity, including any movement or exercise throughout the day. 

Basal Metabolic Rate

The amount of calories your body needs at rest and to perform these functions differs for each individual. Your basal metabolic rate refers to the minimum amount of energy (calories) your body needs to sustain itself at rest. 

Total Daily Energy Expenditure

Another helpful term to understand is total daily energy expenditure. While you need to eat at least the number of calories your BMR indicates you require, you will need a lot more if you are physically active.

Your TDEE indicates how many total calories you burn in a day. When trying to lose weight, you can increase your energy expenditure through exercise. Athletes who train for long hours will have a very high TDEE, but the average person engaging in moderate exercise may not burn enough calories to make a difference in body weight. 

Breaking Down Popular Myths

Now, we’ll address some common questions and myths about metabolism.

Can you have a naturally slow or fast metabolism?

Now that you know that metabolism is simply a cellular process that creates energy, think of it more in terms of BMR. 

A fast metabolism may indicate a high BMR, while a slow metabolism may indicate a low BMR. With a high BMR, you need to consume more calories just to exist, so if you know someone who seems to eat a lot but doesn’t gain weight, they could have a high BMR. A lower BMR means you need fewer calories to sustain yourself, so it may be easier to eat more than you burn. 

That is why equating larger bodies with slower metabolisms is a myth. Research shows people with obesity tend to have higher BMRs. 

Here is a brief explanation of factors influencing BMR.

• Body Composition: Although people with high body fat often have high BMRs, people with more lean muscle than fat may have even higher BMRs. Muscle mass requires more energy than fat. 
• Assigned Sex at Birth: People assigned male at birth tend to have higher BMRs than those assigned female at birth because AMAB people often have more natural muscle mass.
• Genetics: Genetics plays a significant role in BMR, but research is mixed on why,
• Metabolic Syndrome: Metabolic syndromes can alter your metabolism. These are a group of conditions that include symptoms of high blood pressure, blood sugar and cholesterol. 

Does your metabolism slow down as you get older?

Age is another factor that plays into metabolism, and the answer is: maybe. As adults age, they naturally lose muscle, which could lower their BMR, slowing down their metabolism.

Are certain foods good or bad for metabolism?

Some research indicates that consuming caffeine, Green tea, and chili peppers speeds up your metabolism. The studies show they may only slightly boost it for one day after consuming these items and won’t make much of a difference overall. 

Eating more protein offers many benefits, one of which is that it may boost your overall TDEE. Higher protein diets are associated with increased thermogenesis — it requires more energy to digest, so you burn calories just to digest and absorb protein-rich foods.

Drinking plenty of water may also boost your TDEE, as there is a theory of water-induced thermogenesis. Like protein, drinking lots of water requires your body to burn more energy. 

There are no foods that are inherently bad for metabolism. 

Can I speed up my metabolism with exercise?

People with more skeletal muscle mass tend to have higher BMRs. Theoretically, building lean muscle mass through strength training and nutrition has been reported to increase your BMR, but recent research has been mixed on how true this is. 

Regardless, adding more movement and structured exercise to your day requires your body to create and burn more energy. Your TDEE will be higher, though your BMR may not change.

Metabolizing the Truth

Exercising regularly, drinking water, sleeping well, and eating a healthy diet with plenty of protein can all benefit your heart, bone, and mental health. These factors may also influence your basal metabolic rate and energy expenditure. You can’t go wrong with adding more healthy habits to your life, but much information about metabolism is inconclusive.

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