Despite the near-daily references in mainstream media and the fitness industry at large, the metabolism is still one of the most widely misunderstood systems of the human body. Most people don't even know what their metabolism actually is, yet it is still used as an excuse or explanation as to why someone looks the way they do...
Ask the average trainee about metabolic function, and they will throw around questions and statements like:
“Doesn’t green tea speed that up?”
“Isn’t that how much food you can eat and not get fat?”
Or, better yet...
“I don’t have to worry about it, my fat burner speeds it up.”
If only it was that simple!
By the end of this article, the fundamental message I want you to take home is to stop thinking about your metabolism like it’s an “ON/OFF’ switch that certain foods or fads can simply dial simply up or down.
The truth is, that your ‘metabolism’ isn't a single switch but instead, it refers to the functions of the thyroid gland and the Hypothalamus-Pituitary-Thyroid Axis (HPT Axis), which all work in unison to regulate your bodies energy demand in real time through a highly complex hormonal web.
It's not a switch...
It's an entire network of information lines receiving live information on positive and negative feedback systems.
So...This article will cut through the over marketed and overwhelmingly misunderstood concepts of how your body produces cellular energy, and instead, it will illuminate what the actual impact on your training is like when your metabolism is underperforming.
But first, let's get some of the basics out of the way and discuss what the HPTA is, how it works and why it's important.
The Thyroid gland works with given instruction from the Hypothalamus as it produces Thyrotropin-Releasing-Hormone (TRH), which then stimulates the Anterior Pituitary Gland to produce Thyroid Stimulating Hormone (TSH), which then works directly on the Thyroid Gland itself to start churning out the parent Thyroid hormone Thyroxine (T4).
Hypothalamus produces TRH → TRH stimulates Anterior Pituitary Gland (APG) → APG produces TSH → TSH stimulates the thyroid to release T4.
T4 is then liberated into the bloodstream and travels to cells all over your body including muscle tissue and organs, where it attaches to Nuclear Receptor Sites and is then converted to the far more potent Thyroid hormone known as T3, and finally T2.
T3 is 10 times more potent at burning fat/utilising nutrients than T4.
And then T2 is more potent than T3... more on it in a second.
Basically, as you move down the chain of the Thyroid hormones from T4 to T3 to T2 the lipolytic action increases and it is this mechanism that then dictates the rate at which your body produces cellular energy, and by the same token, what your caloric intake must be to provide said energy.
To clarify that a little further and to use a car analogy...
You cannot rev the engine without filling the tank more regularly!
Still not sure where the thyroid comes into play here?
Well, in real-world terms, if you slow down the food intake, the engine must slow to adapt accordingly. The food we eat is 'filling the tank' and the Thyroid revs it's engine according to fuel availability.
More fuel equals a higher performing engine!
Which is how chronic under eating can cause as much weight gain as overeating can.
In essence, with a reduced caloric input, the performance of your Thyroid becomes reduced also. In doing so, you begin to burn fewer calories than what you were prior, your basal metabolic rate (BMR) shows dysfunction and the potential for fat and fluid accumulation increases.
This disruption of input impacts homeostasis, which by definition, means your body is 'out of sync' and this is where negative adaptations (such as a reduced BMR) can occur.
Now, what happens when your Thyroid underperforms due to poor nutrient availability and what does it do to your training?
A sluggish Thyroid can lead to digestive issues, gut health dramas, elevated cortisol levels and it can negatively impact hormonal balancing as well.
In particular, a sluggish thyroid can even increase estrogenic activity.
This sluggishness of the Thyroid is a result of either incorrect conversion pathways of T4 into Reverse T3 (rT3), which is actually metabolically inactive and binds up free T4, or due to actual issues with the signaling to the Thyroid to produce more hormones.
Causation aside, if you throw together that cocktail of gut health issues with elevated cortisol and increased estrogenic activity, essentially your training results can go from hero to zero scarily fast!
Whether it is building muscle or burning fat, both require a certain degree of homeostasis, yet this is thrown out of balance when the Thyroid slows your cellular energy production.
Muscle building has its own huge energy demands in the actual process of synthesising new muscle tissue. The amount of energy needed to build new muscle tissue from scratch is a very metabolically taxing process for the body.
Hence why all muscle building programs involve concomitant caloric surplus!
By the same token, to efficiently burn fat you need the lipolytic activities of your Thyroid hormones to be doing their job, thereby stimulating AMP-K and PPar pathways to name but a few, and encourage adipose tissue to be burnt as fuel.
So very quickly the picture becomes clear that if your Thyroid isn’t producing cellular energy efficiently, then muscle building will be compromised as nutrient uptake and digestion is hampered, whilst fat loss is slowed by the inadequate lipolysis being signaled to take place by your sluggish Thyroid.
Now like all systems in the body, there are negative feedback loops and a slow system also backlogs certain other biological processes in the process.
Keeping it rudimentary, a slow system affects everything from your appetite via the actions of Ghrelin (hunger-stimulating hormone), you rate of digestion and nutrient delivery/partitioning, the elevation of Cortisol as the system is under duress from an internal energy crisis, and finally the elevation of Estrogenic activity due to the decreased metabolic activity coupled with high Cortisol.
Insulin sensitivity will also suffer. But let us look closer at Cortisol!
With Cortisol increases alone you will see increased visceral fat storage while promoting muscle wasting, anxiety, and insulin resistance. This is a potent cocktail for gaining fat and losing muscle!
Estrogenic activity is the next issue for both the guys and gals!
Gender aside, your ratio of Testosterone to Estrogen is referred to as your Androgen ratio.
More Testosterone leads to increased muscle mass, burning more fat, and increased metabolic activity.
Ergo, a slow Thyroid promoting excess Estrogen decreases this ratio, resulting in fat gain, increased fluid retention and decreased Thyroid hormonal output.
Again, this will really put a handbrake on your training progress!
Finally, your gut health is widely recognised now as being a crucial part of the picture for overall health, and especially training progress.
You are not what you eat, but rather, what you absorb!
Your gut wall is 400 square metres, making it the largest organ in your body, which regulates hormones, nutrient partitioning, and brain chemistry.
All of these factors obviously will really slow training progress if they are out of alignment!
So…Let’s address what can be done to help this scenario from never preventing you hitting your next PB in the gym ever again!
Correcting a Sluggish Thyroid:
There are several mechanisms to correct a sluggish Thyroid with the most acute treatments being supplementation.
- Supplements that may help correct Hypo/Hyperthyroidism include adaptogens like Withania/Ashwagandha, Coleus Forskholii, Yerba Mate, as well as vitamins, minerals and trace elements such as Selenium, Iodine, Zinc, Magnesium, Chromium, Vit D, Vit A, Vit K, the B Vitamins, and Tyrosine.
These herbs, vitamins and amino acids work to correct the activity of Thyroid hormones from TSH to the more metabolically active forms T4, T3, and T2 as well as correcting any signaling issues that would otherwise prevent TSH stimulating the production of a healthy amount of T4.
These supplements can, of course, all be sourced individually, or they can all be found in one supplement with our new Thyroid health product, Metabolyz, in the exact doses your body requires!
- In a longer-term approach, there are mountains of data showing resistance training at an intensity of 70% and above (measured usually by heart rate) will elicit the most drastic increases in metabolic activity, including increases in serum T4 and free T3 (1).
- Nutrition, of course, plays a major factor as there is massive nutritive demand in the Thyroid conversion process as mentioned above, so a diet high in nutrient-dense foods is crucial to allow efficient Thyroid function.
- Finally, calorie intake is a powerful tool as well. As discussed in the body of the article, undereating for your energy requirements is a great way to slow your metabolic rate. Inversely, ensuring you consume as many calories as your body requires in a day will ensure you will keep your metabolic rate at a happy rate while you attempt to progress your training goals.
This will have the most profound impact on metabolic health, however, given some of these down regulations are unavoidable during deficit dieting, we have focused on the aforementioned 3 strategies first as they can be used to support the system in times where raising calories may not be possible or advantageous to your goals.
Let’s wrap this up…
A sluggish thyroid may lead to increased fat storage and can compromise your ability to build and repair muscle.
This can be corrected with supplementation, nutrition, and exercise and will lead to fantastic improvements in energy, fat loss, muscle building and hormonal balance, ultimately making progress in body composition a much easier process!
Exercise Intensity and Its Effects on Thyroid Hormones, Ciloglu, F. Et al, Neuroendocrinol Lett 2005; 26(6):830–834