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Metabolism; what is it? Well, it’s one of these most fundamental concepts in biology but also an incredibly broad and complex explanation of everything that happens within you from a metabolic standpoint. You may have heard the term, possibly as part of a conversation about weight or energy, however, the reality of the situation is that there is WAY more to metabolism than you might realise.
Metabolism is the entire series of chemical reactions that are constantly happening within your body that help you to stay alive. Everything from how you convert food into energy, to how your cells keep themselves sustained and repair themselves. Once you understand this concept, many health topics will start to be more tangible.
What Is Metabolism?
Metabolism encompasses every chemical reaction happening in your body’s cells to support life and to allow you to function normally. The word “metabolism” derives from the Greek “metabole,” which means “change.” This is a very good representation of what metabolism does; it is always changing things. Metabolism turns the food you eat into energy. Metabolism builds molecules your body needs to grow and heal from injury. Metabolism also removes waste products that could build up and damage or kill you.
You can visualise metabolism as a city that never sleeps. There are power plants generating electricity, construction workers building or repairing buildings, and garbage men removing garbage, 24 hours a day. The process of metabolism is like all of these activities occurring at the same time at an incredibly small level inside each of your cells. These reactions occur through the use of enzymes (proteins that cause the reaction to occur faster without being used in the process of the reaction) to control thousands of reactions simultaneously by reacting to the specific conditions that exist in your cell.
The Two Sides: Anabolism and Catabolism
Metabolism has two processes that occur at the same time
- Anabolism (building up process of molecules).
- Catabolism (breakdown process of molecules to release energy)
Anabolism is the building up of small molecules into larger and more complex molecules. This is how the body grows new cells, repairs tissue, builds muscle and stores energy for future use. Anabolism requires energy to run. Catabolism is the breaking down of large molecules to release the energy stored in them. When digesting food, catabolic processes release usable energy from carbohydrates, fats and protein, which then help create new cells by supporting anabolic processes. These two are mutually dependent. When they are in balance, they keep you healthy. When out of balance, they can lead to health problems such as muscle wasting (catabolism) or excess fat accumulation (anabolism).
How Your Body Processes Food
The breakdown of food happens in our digestive systems where the carbohydrates are turned into glucose (sugar), the proteins become amino acids, and the fats are converted into fatty acids. These compounds are then absorbed by blood vessels and travel to different cells around your body.
After that happens, glucose begins glycolysis (the breakdown of the glucose molecule) to begin creating energy in cells. The majority of energy generation occurs in the mitochondria (the powerhouses of the cells) via biochemical pathways called the Krebs cycle (named after Hans Krebs).
The final stage is oxidative phosphorylation (the use of oxygen to change energy-rich compounds into energy or ATP) to create ATP (adenosine triphosphate), which is what cells use for all energy.
Fats are the most energy-productive substances in the body, but they take longer to convert. Proteins generate energy, but they are primarily used when a person cannot eat for long periods. Without one, you cannot have the other; either one will create health problems such as excessive fat accumulation or muscle loss when they are out of balance.
Basal Metabolic Rate: Your Baseline
Even when you are at rest, your body has a baseline amount of energy being used. From breathing to moving blood, to your brain staying awake, to all the other processes necessary for life, these require a continuous supply of energy.
The total minimum amount of energy your body needs just to maintain these basic functions while at rest is known as your BMR, or basal metabolic rate (i.e. the number of calories required to maintain the functioning of your body while at rest). Your BMR makes up roughly 60 to 70% of your daily caloric expenditure.
Many different factors affect the BMR: Having more lean muscle mass will cause you to expend more calories at rest than if you had more body fat; therefore, you will have a higher BMR if you have more muscle mass than if you do not.
The BMR typically decreases over time due to a gradual loss of muscle mass as you continue to age. Thyroid hormones regulate the amount of time it takes for your body to perform metabolic activities. Also, genetics play a large role in your BMR. For instance, two identical men of the same height and weight can have a difference in BMR of up to ten percent.
Nutrition and Metabolism
The foods you eat affect your metabolism. Not eating frequently or restricting caloric intake too radically causes slower metabolism rates which will decrease overall fat loss. Eating consistently throughout the day with healthy food aids in the efficient functioning of metabolic processes.
The thermic effect of protein (caloric consumption during breakdown of the nutrient) is the greatest among the macronutrients, therefore burning many more calories while breaking this protein compared to carbohydrates or fat. Building lean muscle through physical activity, especially through resistance training, increases your BMR (long term). If you’re interested in learning more about macronutrients make sure to check out my previous article The Role of Macronutrients in the Human Body!
Conclusion
Overall, life ultimately depends on the function of metabolism in all living organisms; it’s an intricate system that continually transforms food into the energy that your body Needs to operate. This also provides an explanation for why, what and how much you eat will have an effect on you as a person.
At the OsmoHealth Journal, I see that learning about one’s body as among the most important elements of improving your overall health and health science education. Understanding how systems function within, as well as outside of the individual, will facilitate improved support of these systems and their functions along with improvements in physical activity and the studies at large. My hope is that this article will provide you with a foundation to which you can continue building and expanding on.
Stay Tuned for the next article on the OsmoHealth Journal!
References
- Bender, D. A., & Mayes, P. A. (2023). Metabolism. In Encyclopaedia Britannica. https://www.britannica.com/science/metabolism
- Wikipedia contributors. (2025). Metabolism. In Wikipedia, The Free Encyclopedia. https://en.wikipedia.org/wiki/Metabolism
- Bhatt, H., et al. (2022). Physiology, Metabolism. In StatPearls. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK546690/
- Ferrier, D., et al. (2020). Metabolism. PMC, National Institutes of Health. https://pmc.ncbi.nlm.nih.gov/articles/PMC7545035/
- KidsHealth / Nemours. (2024). Metabolism (for Teens). https://kidshealth.org/en/teens/metabolism.html
- Cleveland Clinic medical staff. (2024). Metabolism: What It Is, How It Works and Disorders. https://my.clevelandclinic.org/health/body/21893-metabolism
- Cleveland Clinic medical staff. (2024). Basal Metabolic Rate (BMR). https://my.clevelandclinic.org/health/body/basal-metabolic-rate-bm
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