Metabolism: can you change it?

September 30, 2022

Published: September 30, 2022

Updated: April 12, 2023

If someone can eat whatever they want and never gain weight, often we give credit to their fast metabolism. And if someone else struggles to lose weight, they might blame it on their slow metabolism. Although we talk about metabolism often, researchers still don’t know everything about how it works. But, it’s good to have a basic understanding of what metabolism is and how it and affects your health. In this blog post, we’ll go over what you need to know.

What Is Your Metabolism?

Your metabolism is the natural process in which your body converts what you eat and drink into energy. It happens in all of your cells and is going on at all times. Your basal metabolic rate (BMR) refers to the number of calories your body uses to carry out basic functions, such as breathing, growing and repairing cells, and digesting food. In other words, your BMR is the number of calories your body uses during an average day (not counting exercise). Out of your organs, your brain, liver, kidneys, and heart burn the highest number of calories.1

Factors That Affect Your Metabolism

There are a lot of things that can impact your metabolism. These are some of the most important ones:

  • Body size and composition
    People who are larger and have more muscle mass burn more calories than those who have a smaller body and have less muscle. In other words higher body weight correlates to higher calories burned, while a smaller body burns fewer calories.2
  • Sex
    Men typically have a higher basal metabolic rate than women. This is because men tend to have less body fat and greater muscle mass than women.3
  • Age
    Your resting metabolic rate will naturally slow down as you age. It is a misconception that our metabolism drastically decreases after our 20’s. In fact, a 2021 study showed that metabolism increases up to age 20, then stabilizes from 20-60 years, and then gradually declines.4
  • Diet
    Your metabolism increases when you eat because it takes energy to digest and store food. This is known as the thermic effect of food, or TEF. Eating protein increases your metabolism more than eating carbohydrates and fat.5 This also means that eating fewer calories doesn’t necessarily mean you will lose weight.
  • Exercise
    Exercise is one of the most important ways to influence your metabolism and overall health. People who exercise more often and are more active in general have faster metabolisms than people who live a sedentary lifestyle. As we age past about 50 years, our metabolic rate can decrease by as much as 10% every decade if we don’t protect our muscle mass with strength training!6 Having a higher muscle mass is associated with decreased risk of all cause mortality.7 Aim to strength train all muscle groups at least 2 times per week.8 If you are uncomfortable with the idea of lifting weights, working with a trainer can help you do it safely and effectively.

Calculating Your Metabolic Rate

Now that you know what affects your metabolism, you might be interested in finding out what your basal metabolic rate is. It’s possible to get a general idea of your BMR using an online calculator, but this will only be an estimate. 

It is difficult to calculate your exact metabolic rate. If you’re curious, try plugging your age, weight, sex, and activity level into an online calculator for BMR.

Can You Change Your Metabolism?

As we mentioned above, one of the more effective things you can do to increase your metabolism is to start exercising regularly. Exercise, especially strength training, will boost your metabolism. Moving your body regularly, lifting weights, and eating protein will help build muscle, increase fat burning, and raise your BMR.

If weight loss is your goal, it’s important to be aware that drastic weight loss can actually slow your metabolism. This is because being in a calorie deficit can cause muscle loss if we aren’t getting enough protein and protecting our muscle mass with strength training. Additionally, it takes less energy for a smaller body to function than a larger body, so your metabolism doesn’t need to work as fast.9

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Mythbusting

Because there is still so much we don’t understand about metabolism, there are a lot of things that you might have heard that are actually incorrect. Let’s go over some common myths about metabolism.

  • You are experiencing weight gain because your metabolism is slow.
    This is only partially true. You can’t completely blame weight gain on a slow metabolism – how many calories you’re consuming relative to how many you’re using in a day is much more important. When consuming more calories, it is important to balance this with physical activity. It is rare, but some medical conditions, such as Cushing’s syndrome and hypothyroidism, may slow your metabolism and cause excessive weight gain.10,11
  • Taking certain supplements can speed up your metabolism and lose weight.
    There are a number of products on the market that claim to boost your metabolism. These don’t work, are not regulated by the FDA, and may even be dangerous especially to your liver. It is not recommended to take these.12
  • If you have the same body size and composition as someone else, you will have the same metabolism.
    This is one thing we don’t understand about metabolism. Two people with similar body composition can still have a very different metabolic rate, and it is unclear why.
  • Eating spicy foods and caffeine will boost your metabolism.
    Caffeine and spicy foods may boost your metabolism by a very small amount, but hardly enough to notice. There may be some unwanted side effects from both of these options as well.

Key Takeaways

How the metabolism works is a lot more complicated than it seems and there is still a lot we don’t know about it. There are several factors that can affect it, including your age, sex, and activity level – especially strength training and muscle mass. While there isn’t much you can do to change your metabolism, understanding how it works is an important tool to have. Having a general idea of your BMR and calorie intake can help you follow a healthy lifestyle and manage or lose weight.

References

1. de Nava ASL, Raja A. Physiology, Metabolism. StatPearls Publishing; 2022.

2. Zurlo F, Larson K, Bogardus C, Ravussin E. Skeletal muscle metabolism is a major determinant of resting energy expenditure. J Clin Invest. 1990;86(5):1423-1427. doi:10.1172/JCI114857

3. Arciero PJ, Goran MI, Poehlman ET. Resting metabolic rate is lower in women than in men. J Appl Physiol. 1993;75(6):2514-2520. doi:10.1152/jappl.1993.75.6.2514

4. Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812. doi:10.1126/science.abe5017

5. Calcagno M, Kahleova H, Alwarith J, et al. The thermic effect of food: A review. J Am Coll Nutr. 2019;38(6):547-551. doi:10.1080/07315724.2018.1552544

6. Westcott WL. Resistance training is medicine: effects of strength training on health: Effects of strength training on health. Curr Sports Med Rep. 2012;11(4):209-216. doi:10.1249/JSR.0b013e31825dabb8

7. Li R, Xia J, Zhang XI, et al. Associations of muscle mass and strength with all-cause mortality among US older adults. Med Sci Sports Exerc. 2018;50(3):458-467. doi:10.1249/MSS.0000000000001448

8. Maintain your muscle. NIH News in Health. Published February 25, 2020. Accessed April 12, 2023. https://newsinhealth.nih.gov/2020/03/maintain-your-muscle

9. Farhana A, Rehman A. Metabolic consequences of weight reduction. StatPearls Publishing; 2022.

10. Thyroid and weight. American Thyroid Association. Published September 16, 2015. Accessed April 12, 2023. https://www.thyroid.org/thyroid-and-weight/

11. Cushing disease / Cushing syndrome. Ohsu.edu. Accessed April 12, 2023. https://www.ohsu.edu/brain-institute/cushing-disease-cushing-syndrome

12. Allen P, D’Anci K, Kanarek R. Dietary supplements for weight loss. In: Diet, Brain, Behavior. CRC Press; 2011:167-182.

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