Are Carbohydrates Good or Bad for you? | Muscle & Fitness

— Jason Stoupas

Why do we mostly run carbohydrate biased diets?

This blog is aimed at explaining why we use carbohydrate bias diets in most cases.

There are 4 main reasons we prioritise carbohydrates here at HUSLA: 

• Performance 

• Satiety 

• Thermic Effect Of Food

• Fibre

Each macronutrient has a metabolic cost

The study, “Metabolic efficiency of macronutrient utilisation in humans” explores the fact that energy intake requires more than simply adjusting energy intake to energy expenditure. It requires the separate balance of the three macronutrients.The types of macros you are eating will cost varying amounts of calories to utilise or store.

This is the thermic effect of each macronutrient (1)

• 5 to 10% for carbohydrate

• 0 to 3% for fat 

• 20 to 30% for protein 

The above figures will depend on how much of the nutrient is immediately oxidised (burnt) or stored, with storage being a much more energetically costly process.

Now we know that the breakdown of protein costs the most energy followed by carbohydrates and then fat being last. Fat is the easiest macronutrient to breakdown. This means that protein uses the most calories to breakdown, and fat uses the least calories.

Total energy used to store each macronutrient varied as follows (2):

• Carbohydrate to glycogen:
  3 to 5%

• Carbohydrate to fat:
  28% 

• Fat to fat:
  7%

• Protein to glucose to glycogen
  24% 

This means that the most energy is used when trying to convert carbohydrates to fat.

This could mean that if you are prioritising fat in a surplus there is the potential to gain fat when it hasn’t been utilised. Carbohydrates on the other hand, will either be converted easily to fuel and if any of it needs to be stored as fat 28% of the calories will be burnt in the process. 

When comparing fats and carbohydrates we can see that with a high-carb diet we will increase the overall impact of the Thermic Effect of Food on Total Daily Energy Expenditure (TDEE). This means that less calories will go towards storing fat.

With the above information we can assume that a diet that prioritises protein and carbohydrates will increase the thermic effect of food and therefore increase TDEE. Although TEF may assist in increasing energy expenditure, don't put all your eggs in one basket.

So if it's such a small piece of the puzzle then why do we use carbohydrate biased diets?

Well, we know that our body's preferred fuel source is dictated by the rate at which ATP is needed. (ATP is our body's source of energy) During maximal efforts our energy systems are used to provide our muscles with energy to lift weights. All energy systems are working at all times. They work to provide energy for everything that we do. If we assume maximal intensity, then we can safely say that the dominance of each energy system is dependent on duration of effort. 

The below graph shows each energy system and its contribution dependent on duration. The red line shows how performance reduces as each energy system is exhausted. 

Rate of energy for ATP resynthesis:

ATP/PC System 

• Explosive/Instantaneous 3.6 mol/min

Lactate/Glycolysis System 

• Fast, 1.6 mol/min

Aerobic System 

•  Slow - Glycogen 1.0 mol/min 

• Slowest -Triglycerides less than 1.0 mol/min

We don’t need to get caught up on the numbers above too much, all we need to see is that they are trending down as we move through each energy system. This is why we can not perform at 100% forever. Energy simply just can not be produced fast enough. 

I want to bring your attention to the Lactate/Glycolysis System vs the Aerobic System, both of these energy systems use Glycogen as their preferred fuel source (broken down from carbohydrates) the Aerobic system can also use fats as energy but that is much slower than the Aerobic system’s ability to produce energy from glycogen.

The Anaerobic systems produce ATP much faster than the aerobic system. This is why we want to eat the fuel that our dominant energy system utilises!

This is to improve performance, to get those last reps out and allow you to perform better, grow bigger and get stronger. 

Now don't get me wrong, if you are fuelled by a fat dominant diet you can lift weights and still make gains, but you will not be able to perform as well as if you were eating carbohydrates. 

This brings me to my last reason for carbohydrate bias diets… satiety! 

What  is satiety?

Satiety is a feeling of being full. Some foods make us feel fuller than others.

Some foods can be cooked differently to make us feel more full or less full. That’s something that we want to be aware of when trying to lose fat. 

When comparing our 2 fuel sources, fat and carbs, we can safely say that fat is quite easy to consume in high calories whilst still not feeling full. 

Whereas carbohydrates in the form of potatoes contain less calories and can leave you feeling more full than fats.

The below graph shows some of the most calorie dense options for fats and carbohydrates. It also shows some of the most satiating fat and carbohydrate dominant options. 

The below graph indicates how more food volume can be consumed with the foods on the right compared to the left.

The general guidelines which we use here at HUSLA: 

Protein: 1.8 - 2.2g per kg of bodyweight. Important for muscle building and also very important for satiety 

Fat: .7 - 1.3g per kg of bodyweight (studies support going as low as .5 but you may lose the ability to get a range of fats into your diet comfortably) we stick to .7-.8 minimum for most. Plus eating super low fat and high carb can be difficult and boring if the client has not built a quantitative nutritional awareness.

Carbohydrates: We gauge average weekly energy expenditure and from there we average that out to a daily figure. After calculating protein and fat with the above figures we can then find out carbohydrate recommendations being the left over calories.

Fibre:

15 - 18g of fibre per 1000 calories consumed and Should aim for approx 70% of that fibre to come from vegetables.

EG. 2000 calorie maintenance we would advise to aim for 30 - 36g fibre per day. This can be hard initially but once the skill is acquired and with experience it will become a much more diverse and transparent experience. With some practice spreading your foods out and making meals with fibrous ingredients, it’s actually not too hard!

Fibre is highly satiating and fibre is a carbohydrate, this is another reason why we bias carbohydrates, to meet fibre targets more easily.

To wrap this up, carbohydrates are more filling, they use more energy to burn and improve performance when prioritised. This is not the answer to everyone's problems but, it sure does go against plenty of things that have been said about carbs in the past. I'm NOT saying you MUST eat heaps of carbs. This is why we use it in most cases and if you have been prioritising fats and think that you may benefit from the things listed above, then maybe have a think about shifting things around.

Thanks for reading guys, if this helped or you have any questions please reach out, I would love to hear from you :)

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Reference list

1. Westerterp, K.R. Diet induced thermogenesis. Nutr Metab (Lond) 1, 5 (2004). https://doi.org/10.1186/1743-7075-1-5 

2. F. Xavier Pi‐Sunyer M.D. (1993) Metabolic efficiency of macronutrient utilization in humans, Critical Reviews in Food Science and Nutrition, 33:4-5, 359-361, DOI: 10.1080/10408399309527633

— Jason Stoupas