Unreleased Guides

Metabolic Health Explained - The Role of Your Metabolism

Henrietta Paxton

Head Nutritionist at Biospan (MBANT, CNHC)

Unreleased Guides

Metabolic Health Explained - The Role of Your Metabolism

What is metabolism?

Please note - this guide has not been referenced, because it was created as an internal document to share among team members. However, people have found this valuable - so we have decided to release it as a free guide for the public. All the information was created by specialised nutritional practitioners who are trained in evolutionary science and functional medicine.

First let’s define what we mean by metabolism. People like to use this word a lot in terms of having either a “fast” or “slow” metabolism, but what are we actually referring to?


noun - The chemical processes that occur within a living organism in order to maintain life.

So we are talking about the whole range of biochemical processes that occur within us(or any living organism) and also (but not exclusively) the chemical reactions in the body's cells that change food into energy. Our bodies need this energy to do everything from moving, to thinking, digesting, and growing. The term "metabolic" is mostly used to refer specifically to the breakdown of food and its transformation into energy. This may seem that “metabolic” only then refers to this one specific action (food to energy) but if you consider the numerous processes needed to get actual whole food into an energy molecule in the body “metabolic” encompasses, and goes onto impact, every single bodily process.

And yet we Typically think about energy in relation to simply having enough energy for movement, exercise, and sport. However, we are missing the fundamental point here that nearly every reaction in the body from digestion, thinking, and detoxification requires energy to work. So, the energy we get from food is needed to be able to think and decide where we are going to get that food; physically getting the food; chewing, properly digesting and absorbing that food; detoxifying and excreting what we don't need from the food; transporting the nutrients where they are needed in the body; and only then, eventually, making energy from those nutrients that we got from the food.

Suddenly "metabolism" and "metabolic health" it is not so simple as just turning food into energy.

What is energy?

“Energy” refers to the ATP molecules that we use to give any given reaction its required energy to make it happen. So, we are certainly not just talking about muscle contraction and movement, we are talking about pretty much every single cellular reaction in the body. 

How do we make ATP molecules?

Through a complex process called the Krebs cycle or the citric acid cycle (TCA cycle) whereby we turn Acetyl CoA into ATP.

What is Acetyl CoA 

This is the only molecule that can enter the Krebs cycle, so while we think of using “glucose” or "fat” for energy, both must first be transformed into Acetyl CoA, by means of beta-oxidation in the case of fat, or through turning glucose into pyruvic acid in the case of glucose. We can also use protein when needed to make Acetyl CoA. 

The process of turning any one macro nutrient (fat, protein, or carbohydrate) into an ATP molecule is highly dependent on the availability of a plethora of micronutrients – Iron, magnesium, B-vitamins, biotin, vitamin C and Coenzyme Q10 to name just a few.

Where do we make energy? 

This process happens in the Mitochondria which are like the powerhouses in every cell. We can compare healthy functioning mitochondria to a wind farm and unhealthy damaged mitochondria to a power station using fossil fuels. Both produce energy – however one does so in a sustainable “clean” way while the other produces toxic by products. In either one of these the substrate (wind or coal) is taken in and through multiple processes produces energy.

In the mitochondria the substrate (glucose, different fatty acids, or amino acids) are taken in, turned into Acetyl CoA, and ATP molecules are produced. Mitochondria are present in every cell of the human body apart from red blood cells – that’s how crucial energy generation is. Depending on which substrate we use to make the acetyl CoA subtly changes the outputs from this reaction that can either keep it working perfectly well overtime or create “toxic waste” that needs to be dealt with. Much like a wind farm versus a coal power station.

How are mitochondria related to health? 

The function of how we make energy in the mitochondria can be compromised by a variety of things; 

  • Because the mitochondria themselves are damaged (through oxidative stress - see below) 
  • If we continually use the wrong substrate to try to make energy (fatty acids from seed oils)
  • If we lack the micronutrients to turn the wheels of the machine efficiently (nutrient-poor diet) 
  • If we generate too much toxic waste from trying to make this energy and not enough clean up molecules (nutrients deficient diet) 
  • If we push too much substrate through the Krebs cycle (calorie dense and nutrient deficient diet i.e. processed food) 

We are then at risk of a huge variety of cellular reactions and bodily processes being compromised because we cannot energise them properly– not just fatigue or energy crashes, but dysfunction caused by poor metabolic health i.e Metabolic dysfunction.

Metabolic Health 

So, therefore, when we talk about metabolic health, we are referring to; 

  • The nutrients we have available (both macro and micro) to use in the Krebs cycle
  • The amount of substrate we are trying to push through the Krebs cycle 
  • The health of our mitochondria 
  • The number of mitochondria we actually have 
  • The efficiency that we can turn these nutrients into energy 
  • The by-products created in making the energy (both helpful and toxic) and how we deal with them

What is Oxidative Stress 

One of the major outputs of energy generation is a molecule called reactive oxygen species (ROS). These molecules are highly reactive (as the name suggests) and in the right amounts these ROS act as signaling molecules that regulate the Krebs cycle process. The mitochondria can generate their own antioxidants to “quench” the action of the ROS once their job is done. This is called redox balance. Balancing between allowing some reactive action of ROS and stopping that action when needed.

Redox Balance

When this redox status is out of balance (i.e. we are generating more ROS than we are anti-oxidants) the ROS start doing damage to the molecules and cells they come into contact with including damage to the mitochondria themselves, which then impacts their efficiency and ability to generate energy. This causes increased production of ROS in relation to ATP and further increases ROS damage. This leads to a situation of “oxidative stress’” to which the body responds with its immune system, the first line of which is inflammation.


Inflammation is essential to mandating life through being our first line of defence against infection or injury. It is critical that we can become inflamed, but it is equally critical that when the inflammation has done its job (killed the bacteria or pathogen, or the damaged tissue from an injury) hat it is switched off. 

Low level, uncontrolled and unresolved inflammation is the basis for, or has a role in, pretty much every single chronic disease we know about, including heart disease, type 2 diabetes, auto-immunity, and high blood pressure. Therefore “metabolic dysfunction”, whereby energy production on a cellular level is essentially broken and toxic, leading to redox imbalance, oxidative stress and then inflammation can affects every single bodily function, like blood transport and pressure, like the health and regeneration of the cell linings of our arteries, and eventually how we are able to use and store the energy substate in the first place (fat or glucose). This is the concept being referred to as “metabolic dysfunction”.

Back to Metabolic Dysfunction

The reason diet plays such a central role in metabolic dysfunction is because it is from what we eat that we provide either the right type of substrates for the Krebs cycle or not (both macro and micronutrients). Certain types of foods and fats as well as too much substrate (too much food) trying to enter the Krebs cycle to be used for energy breaks this process – leading to metabolic dysfunction and then all the downstream chronic diseases.

This is increasingly recognised as having huge impacts on the outcome of covid 19 infection. This is why we see people with “underlying health conditions” being disproportionally affected by the infection and having much worse outcomes. For “underlying health condition” you can essentially read “metabolic dysfunction” – Type 2 diabetes, Alzheimer’s (also known as type 3 diabetes) and CVD being the ultimate (but not only) expression of metabolic dysfunction.  We have seen concern expressed by the government for those with Type 2 Diabetes in relation to covid infection but without any explanation from the government as to why they are at risk. It is the metabolic dysfunction that is leading to the poor covid infection outcomes. 

Metabolic dysfunction and Covid 19 infection 

This type of redox imbalance, presence of pro-inflammatory nutrients in the diet and - pro-inflammatory state seen in metabolic dysfunction appears to play a huge role in the “cytokine storm” (massive over reaction of the inflammatory part of immune function) in response to coronavirus infection that can eventually lead to death. Your bodies own immune system is so dysregulated and overactive it kills itself. 

What is truly empowering though, and sadly not being talked about enough, is the power we have to change this through food and lifestyle. Whilst the vaccine may help our immune system to deal with this particular virus, it is having no impact on the underlying cause of the problem, which is metabolic dysfuntion.

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