It’s Bigger Than You Think
If you type ‘Metabolism’ into Google the first definition to come up is one from the Mayo Clinic taken from the page Metabolism and Weight Loss. Out of 772,000,00 results the first sentence on the term reads “Metabolism is the process by which the body changes food and drink into energy.” This definition sounds like a simple exchange between the food and body.
Yet if I open the pages of my Human Anatomy & Physiology textbook (Marieb et al.) Metabolism would be described like this “ Metabolism (me-tab-o-lizm; “a change of state”) is a broad term that includes all chemical reactions that occur within body cells” Human Anatomy & Physiology
a broad term
That’s because systemically metabolism is a far greater process than what we are led to believe through health marketing and diet/fitness industry discourse. I would actually argue that for most people the term metabolism would stand for little more than the villain in a story - one that acts too fast in those trying to bulk and too slow in those trying to lose weight - with little more to the term.
What it looks like
I get to take a slightly unique perspective here because my background, pre Nutrition, was as a Nuclear Medicine Scientist. My job was to use radiopharmaceuticals to image the metabolic process of the body.
Below is a video of a PET scan where the patient has been injected with a sugar (glucose - the primary fuel for the body) which was tied to a radioisotope before injection. Meaning we are able to image and track in real time where glucose travels within the body and how it behaves within all human cells. This is metabolism.
What you’re viewing in the above video is radioactive sugar being utilised as energy within the body. The areas which are brightest are the cells which turn over quickest, they are the most metabolically active. These include our brain and liver but eventually it will be utilised by the whole body, feeding every cell so we can continue to function.
It’s a beautiful thing. Metabolism isn’t the villain, metabolism is the hero.
Marketing Metabolism
It is to no fault of the general population that our understanding of the term Metabolism is so reductive. It is through our conscious effort to be nutrition and health conscious individuals that we take on such terms and the ever changing information around them to try and better ourselves. A near impossible task with the never ending changes to nutrition advice and recommendations from “boosting your metabolism”, to superfoods, to weight loss, to gain muscle, improve gut health, heart health, better your skin, better sleep, lower blood sugar, get enough protein, making sure you don’t have too much protein, above all to remain in a physique that fits societal standards - it’s a lot.
It is well studied that capitalist economies, like Australian, thrive on the marketing of health as it makes the consumer feel they are improving one's self, providing a sense of empowerment to the consumer who believes by consuming a certain product they are preventing something bad from happening to the body. Marketing health provides a framework to consumers which aligns with social and cultural expressions of morality, “.. the concept of health is a way people give, expression to cultural notions of well-being or quality of life, and that talking about health is a way to reaffirm shared values of a culture and express what it means to be a moral person.”
With ‘health’ being such a huge driver of the food and diet industry it is no wonder we see the oversimplification of broad terms. Medical, scientific and functional words are sexy - even if we don’t quite grasp what they mean. Metabolism, of course, is one of them.
Greater Implications
I know I personally grew up hearing the term in reference to my body, my understanding of why I could not lose weight was that my “metabolism was broken”. This understanding of course taught me nothing of how to eat but did teach me a lot about how untrustworthy my body was. In fact, the internalisation of this message resulted in the opposite of its generic understanding and created an absence of health. As my understanding of my body was met with shame and disappointment I fell into disordered eating behaviours, compared myself to those with a seemingly “fast metabolism” and became disconnected from my body.
consumers become burdened with food-confusion, angst and anxiety over the pressure to eat in a way that is socially acceptable. Therefore creating a reliance on marketing, reductive dietary guidelines and also professionals to tell you what it is you should be eating.
This reductionism of the body, the relationship of food and the body, impossible volumes of nutrition advice and ever changing scientific information around nutrition has ultimately created a framework around eating which deifies anything regarded with the term ‘health’ and removes our knowledge of our bodies. In understanding food this way, consumers become burdened with food-confusion, angst and anxiety over the pressure to eat in a way that is socially acceptable. Therefore creating a reliance on marketing, reductive dietary guidelines and also professionals to tell you what it is you should be eating.
Your Metabolism Doesn’t Concern Itself with Societal Standards
Sorry to tell you this - Your metabolism serves the purpose of keeping you alive over ensuring whether you fit in with the latest body trends. It actively doesn’t want you to starve - which for hundreds of thousands of years was a very real threat to human existence. Your metabolism wants to maintain good bodily function so you can thrive and to maybe even store a little fat so you’re protected in times of famine (kinda like those times you keep dieting). It’s funny how a function of our bodies we are so incredibly blessed with is often the thing we fight so stubbornly against.
The phrases most often associated with metabolism marketing are “boost your metabolism”, “reset your metabolism” and “starvation mode”. All of course, tell you that you, your body, is broken. And likely sell you a product to get it working again.
What all these refer to is likely the down-regulation of metabolism that comes with long term dieting, this is a thing. The down-regulation, or slowing down, of metabolism is a survival mechanism. It is a subconscious and deeply evolutionary effort of your body to reduce energy output when energy input (calories) have been too low for too long. This looks like having less overall energy, fidgeting less, less animation when talking, blinking less, the slowing of both cardiac and respiratory rates and in advanced cases the atrophy of organs. Your body is actively trying to pull you out of the energy deficit to keep you alive. The only way to “reset” the down-regulated metabolism here is to up-regulate it through the reintroduction adequate energy (calories).
So… Should You Be Paying Attention to Your Metabolism?
Well, it depends.
In the context of dieting it is important to understand the energy input and energy expenditure in order to make educated guesses about what a deficit or surplus would look like. However, I do say “guesses” because the equation to calculate this is not quite so black and white as energy input and output (calories in vs calories out).
The very basic equation for this looks more like -
Energy Ingested (actual calories in (understanding nutrition labels and tracking apps are inaccurate) - calories absorbed (because all food absorption rates vary) - Total Daily Expended Energy (Basal Metabolic Rate + Thermic Effect of Food + Physical Activity + Non Exercise Activity Thermogenesis)
So really the best we can do is educated guesses through observing data and which way the trends lean in relation to your desired outcome then adjusting accordingly i.e increasing or decreasing calories, steps, exercise etc. Understanding Metabolism in terms of how much energy (calories) we could consume is a really good starting point when looking at nutrition. But given the ambiguity of the calculations observation and adjustments are required which is where a professional might come in handy. In terms of increasing it there are absolutely methods to do so through gradually building calories, increasing muscle mass through resistance training, increasing daily activity through walks.
Have I ever used such a nuance of increasing someone's green tea consumption to ‘boost metabolism’ even some into my practice when dieting someone down or removing it from someone's diet when trying to gain weight? Absolutely not.
In Conclusion
Metabolism is not an ambiguous phenomenon working against you, but rather each and every chemical reaction within your body working to keep you alive. While a large portion of these reactions is reliant on the exchanges between food and the body, it is not everything. A broad term. The reduction of the system within marketing serves one purpose - to remove trust in yourself and body. By creating distrust in our bodies we, as consumers, are reliant on professionals and products to fix us. Thus we buy into supplements, diets and other gimmicks which promise to fix our "inherently broken" bodies. Then when these products fail to work long term it is our bodies we blame and the distrust deepens.
Let's learn to love yourself & food
Notes
Mayo Clinic, S. (2022) Metabolism and weight loss: How you burn calories, Mayo Clinic. Mayo Foundation for Medical Education and Research. Available at: https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/metabolism/art-20046508
Marieb, E.N. and Hoehn, K. (2014) Human Anatomy & Physiology. ninth. Harlow, Essex: Pearson.
Mudry, J. et al. 2014 “Other ways of knowing food” Gastronomica, 14(3), pp. 27–33. Available at: https://doi.org/10.1525/gfc.2014.14.3.27.
Sharp, A. (2022) “BEST METABOLISM BOOSTER | CAN FOOD AND EXERCISE BOOST OUR METABOLISM?,”
Sharp, A. (2022) “HOW TO FIX A SLOW METABOLISM | REVERSE DIETING VS. ALL-IN,”
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