Carbohydrates are one of the most important chemicals needed for survival. Whilst you CAN produce enough glucose from non-carbohydrate sources, if you intend on exercising and remaining healthy whilst doing so, they become essential.
Carbs serve a plethora of purposes, from keeping blood glucose at a steady state to allowing your muscles to work at a higher capacity. Its consumption allows the extremely important anabolic hormone insulin to come into play (which I discussed previously) promoting protein synthesis thus preventing the breakdown of amino acids (protein) into a fuel source. It serves to restrict the catabolic effects brought about by hypoglycaemia (low glucose) and if you do plan on going “low carb” whilst remaining inactive, that’s fine, but as soon as you start working out is where the problems can start to arise.
The theory is that If you want to go carb free, then you need to up your protein intake to pick up the deficit caused this lack of carbohydrates or else your body begins to breakdown proteins over fats. This is the premise of the much popular Ketogenic diet where carbs are replaced almost entirely (depending on degree of ketogenesis the user wishes) and ups their dietary fats and proteins to pick up the caloric slack. In theory, this sounds perfect, but it doesn’t necessary work like this, going from high carbohydrate consumption in youth and early adult to suddenly restricting carbs does not just suddenly send your body into a fat burning mode, it can become somewhat complicated….
But how does it all work? Well Glycogen is our first readily mobilised storage form of glucose. When energy is needed skeletal glycogen is broken down too produce glucose and fuel exertions. This process of breakdown is initiated by a restriction of insulin and mobilisation of glucagon hormones and once we’ve stopped exercising the reverse process occurs, this process maintains a stable level of blood glucose concentration required between meals or in any fasted periods.
Glycogen is stored in two primary sites, the liver and skeletal muscle (we do also have smaller concentrations in kidneys and intestines). The concertation of glycogen in skeletal muscle depends on LBM (Lean body mass) and the trained state of muscles. The liver stores approximately 70-100g and doesn't appear to vary greatly from this amount.
When we consider energy use the first energy system used during 5-10s any exercise is the ATP-PC system, after this we enter into a glycolysis and oxidative systems. Glycolysis relies heavily on the breakdown of carbohydrates and lasts 10s-2/3mins, so it’s the optimal system used for resistance exercises (body building etc).
Training that requires constant use of the glycolic energy system results in biochemical changes resulting in a higher level of skeletal glycogen being made available for breakdown. The theory of carb loading stems from this premise that by increasing LBM and adaptation of muscles to hold more glycogen stores and then shovelling in carbohydrates before an event (time periods vary per sport) however most studies show that for novice endurance and physique athletes has very little impact on their actual performance.
A brief breakdown:
Muscle Glycogen per 100g of Muscle
Untrained Muscle 13g
Trained Muscle 32g
Carbohydrate-loaded muscle 35-40g
Insulin function, resistance and Carbs
On average, for 10-15 g our body will use around 1 unit (iu) of insulin to manage it and act as the substrate carrier into cellular tissue in its converted form glycogen. At basal level (BMR) the amount of insulin someone produces daily it is typically be divided into 24 units to reflect what is produced per hour. Each meal ingested on top of this will require a further five to six units to be produced. If we consider the average person consuming three meals a day…that’s around 42 units which would mean that around 420-630 g of glycogen is transported into cells. This partly explains the benefit to those with larger amounts of LBM of increased meal frequency.
A large part of the demographic we deal with as clients will be striving for weight loss and undoubtedly already be in a state of diminished glucose sensitive insulin secretion. The absolute level of glycogen they can store in cells will be compromised and the surplus would result in elevated blood glucose levels. If this isn’t addressed, complications such as diabetes can arise.
From what I mentioned above, getting leaner PRIOR to trying to add additional muscle mass will have the benefit of increased glycogen uptake, a large and crucial factor in growth. The leaner someone becomes the more sensitive cells will typically become to the actions of insulin. If you do the math at this stage, you will realise why frequency of meals can play a role when attempting to build more lean tissue and capitalise on the benefits of insulin. This is only relevant however to those that have somewhat maximised cellular saturation of glycogen and volume within their workouts (Those already with a significant amount of tissue). But you can also see the benefit in an increased meal frequency to insulin-resistant populations.
This is again, a very brief overview of Insulin and I’ll cover It in more depth when I continue my blog on metabolic hormones.
Why is this important? Well as a PT when someone asks for a diet plan I’m always somewhat hesitant to give them one, purely because I don’t know what level of insulin resistance they may have especially in women who tend to binge, diet and repeat. Carbohydrates requirements, intake, management and all of the aforementioned factors all come into play when deciding on a carbohydrate intake for someone. The overall level of adiposity (fat mass) and the type and frequency of training. As we can see it is a hugely personal thing with huge variability as what is low carb to me could NOT be low carb to someone else. Someone’s ability to handle carbohydrates from both the stage of ingestion, digestion and absorption varies hugely and this in a nutshell is the take home point here. It's so easy for PT's to just relabel a diet plan that works for one client and just hand it over to another for a costly price. I tell every client i have, the benefits of doing your own brief research outweigh my telling you what to do for additional cost.
Additionally, when shopping for food a macronutrient that is 30% lower or more than its original version can be labelled as ‘low’ or ‘reduced’. This means it’s the same for proteins that be labelled as low fat, or high protein (see halo ice cream). Each time it is contextual as to what the original version of someone’s diet may have been. This is where it’s complicated, especially for me, because when I do inductions or consultations I’ll hear “I’m on a low carb diet” or “I’m on a high fat diet” but that is completely contextual as, just like any macronutrient people desire absolutes with respect to the numbers they are aiming for, as another example “I eat 120g of protein a day” but this is a number generated by an app or website that has no history on you, it might well be enough but it might also be TOO much or NOT enough. To elude that there is an ‘absolute’ number or even ideal is absurd. We have guidelines and from these there is simply a baseline in which to start from.
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