The Carbo-Hack

News Written by Boris Clark

When it comes to nutrition there’s a lot of ways we can enhance performance, improve recovery, and change the response we see to training. When it comes to endurance sports performance, training without proper nutrition in mind is loosely related to banging your head against a brick wall. It’s pointless and you won’t get very far! Obviously doing the training is important, but the nutrition comes in a close 2nd in terms of bang for buck on improving performance. That said, let's jump into the meat of today’s blog.

First up in the blog series is quite possibly THE MOST important (but highly debated) aspect of endurance performance. The fuel. Specifically, carbohydrate (CHO).

So What Is Carbohydrate?

I’ve spoken time and time again about the importance of carbohydrate and how its use can be manipulated to your advantage (Click Here to see that blog). Alas, there is a massive misunderstanding around what CHO actually is.

Forgive me for the chemistry lecture to come, but stick with me and I promise the mist will clear! #nerdalert

At the basic molecular level, carbohydrate is one carbon molecule (C) and one water molecule (H2O). So you can then see where the name comes from, ‘carbo’ (carbon), and ‘hydrate’ (water). If we look at one of the most common forms of carbohydrate we talk about in sports science, glucose, then we see the molecular make up of this is C6H12O6. So the same make up as the one carbon one water molecule described, just here there are 6 carbons and 6 waters. If we look at something like a starch (potatoes etc) then these numbers change a little due to linkages and chains of carbohydrate molecules. This is also why carbohydrate is commonly referred to as CHO, C=carbon, H=hydrogen, and O=Oxygen. I know, I can hear your brain cogs churning from here, but the aim here is to show that carbohydrate is simply one carbon and one water together. This chemical make-up also becomes important to understand if you want to understand other factors regarding lactate metabolism in other more in-depth blogs I’ve written. You’ll be glad to hear that’s the heavy science out of the way. Now we can move on to what carbohydrate actually means for YOUR performance.

Carbohydrate Overview

We get carbohydrate from foods such as bread, pasta, rice, candy, anything made of sugar, and more. What kind of carbohydrate we should eat and at what time will be the topic of a future blog but for now we are going to generalise.

When we eat carbohydrate, it goes into our gut and we absorb it into the blood. Our body then has three options: Use the carbohydrate for fuel now, store it as glycogen in the muscles for later, or store it as fat (also a form of saved for later!).

If we are exercising hard we use the carbohydrates as fuel pretty quickly, but if not, the carbohydrate stays in the blood, leading to high blood sugar levels. This isn’t a healthy state to maintain, so our body then releases a hormone called insulin from the pancreas. Insulin’s job is to allow the carbohydrate to be stored in the muscles for later use (glycogen), or if there is no space for this, then we will store the carbohydrate as fat in a process called de novo lipogenesis. A quick thing to note is that while de novo lipogenesis does happen, the primary way we gain weight through eating excessive carbohydrate is actually because the body prefers to burn excess carbohydrate for fuel first rather than storing it. But if we are burning the carbohydrate for fuel, then we don’t use our body fat for fuel, so the net outcome of increased total fat is still the same. DO NOT think CHO is simply going to be stored as fat! The body will prefer to burn it or store it as glycogen if possible. The main way you gain weight through excessive carbohydrate intake is due largely to less fat burned, rather than storing more fat per se.

So now we know what happens when we eat carbohydrates. But why are they important for performance?

Carbohydrate & Performance

We have two main sources of fuel to power our athletic endeavours. CHO, and fat.

Carbohydrate is the body’s preferred source of energy. We can break it down quickly, there are relatively few rate limiting factors to how much of it we can burn at once and it’s easily accessible for most of us. However, the amount we can store in our body, or take on during exercise, is limited (again, more on this further in the blog series!). On the other hand, fat is virtually an unlimited fuel source, even in extremely lean athletes. The problem is there are several factors that limit how fast we can utilise and burn fat. This is because there are a series of steps we have to go through to turn fat into a useable fuel source. The fat must be broken down from triglycerides to fatty acids and glycerol. The fatty acids must then be removed from the fat cell and transported via the blood, where they are bound to albumin. If all albumin is saturated with fatty acids then it is not possible to transport any more fatty acids. It is then transported into the muscle cell. From there its transported into the mitochondria, which requires carnitine, which is also in limited supply also potentially limiting fat oxidation. The fatty acids are then finally oxidised in the beta-oxidation pathway and TCA cycle, but we must have oxygen available to do this. In short, it’s a lot easier for the body to use blood glucose/glycogen!

What this means in practical terms is that at low intensities we burn a high percentage of fat, as the energy demand is low, and we have time to go through the fat oxidation process. As intensity increases we burn a lesser proportion of fat, as we are asking for more energy quickly, and we must, therefore, utilise a higher proportion of carbohydrate. It’s better not to think of the fuel mixture we are burning as percentages. When we are doing nothing or exercising very lightly we aren’t burning very much of anything (but a higher % fuelled by fat), but as intensity increases we burn both more fat and more carbohydrate because we are burning more energy in total.

I’ve illustrated this in the INSCYD graph below from a lactate test of an athlete we coach at Metabolic Performance Solutions.

The amount of fat and CHO you burn day to day, for a given exercise intensity, can be affected by many things, such as what you’ve eaten, how much glycogen you have stored and how long you’ve been exercising that day. Obviously this is just an estimate in the graph above. But it does illustrate how as exercise intensity increases you need more CHO to perform.

As we mentioned earlier, fat reserves are practically unlimited, while carbohydrate stores may only be able to power around 2h of intense exercise. As you exercise at low intensity you have a large store of fat to burn, whereas at high intensity you can be burning as much as 100% CHO (of which we have limited stores). This means at high intensities you are not only burning more fuel, but the fuel tank of the type of fuel you need also gets smaller the harder you exercise. To quote a good book I’ve read on this topic, “I can only assume this is nature's idea of a joke”.

This illustrates just how important it is to ensure you are getting enough CHO in the system during exercise (and that you can burn fat effectively to spare CHO).

Getting around these problems

This is where specifically formulated sports nutrition, like UpShift’s ‘SUSTAIN’, can help. You’re always going to run into the problem of burning more carbohydrate than you can absorb during high-intensity exercise. But by using a CHO drink (or gel or other food), with the right combination of different carbohydrates, we can hijack our bodies into absorbing more CHO. This is why UpShift Nutrition's SUSTAIN uses an 0.8:1 blend of fructose/maltodextrin, it's ratio shown to provide maximum CHO delivery together with the lowest rate of gastrointestinal distress thus taking full advantage of our body’s abilities. Basically it allows you to go harder for longer.

Stay tuned - In my next blog I’ll be discussing pre-workout nutrition in order to maximise performance

Until next time, happy training.

Boris Clark
Head of Performance
Metabolic Performance Solutions

PS. For those interested in learning more about performance optimisation head to my website

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