What Fuel Sources Do Cyclists Use During A Ride?

When it comes to your nutrition on the bike, understanding what fuels you’re utilising during a ride is critical to understanding your individual needs and developing your own personalised nutrition strategy.

There are two main fuels that we utilise during exercise: carbohydrates (predominately in the form of glycogen stored in the muscles and the liver) and fat.

As athletes, we have relatively limited stores of glycogen (the name for carbohydrates in their storage form), equating to around 2000 kcals or 500 grams of carbohydrate for a well-trained athlete when glycogen stores are well topped up. A key adaptation to training is an increased ability to store glycogen. For any rider who looks at their kj/kcal output after a hard ride, you’ll know that this is a relatively modest amount of energy, and at high intensities, we can rip through these stores relatively quickly.

In contrast, even relatively lean athletes can have more than 80,000kcals of energy stored as fat, owing to the very efficient way that adipose tissue stores energy. This is enough to fuel days, if not weeks, worth of back-to-back exercise.

To a small extent, the body can also break down protein during exercise, although this accounts for only around 5-10% of total energy expenditure and this only really occurs to any meaningful extent in the absence of glycogen, where the liver will convert proteins into glucose to help maintain glucose supply to the brain.

There are a number of factors that can influence what fuel we use at any one time during a ride, from the exercise intensity that we are riding at and our habitual diet to our intake of fuel around the session and the duration/demands of the session itself.

Our use of fuel isn’t static, so what fuels our body uses at the start of exercise, can be very different to what it uses at the end of the ride when our glycogen stores become depleted.

For years, the influence of these different factors has been studied in many published sports nutrition studies. A recent review paper by Rothschilds (and colleagues), a sports dietician and researcher from New Zealand, (which must have equated to a huge amount of work!) has pulled all this data together from a staggering 434 research papers and used a modelling analysis to give us incredible insight into the influence of different factors on fuel use during exercise.

What was really cool about the analysis was that Jeff didn’t just publish the paper but also put together a very useful online application to allow you as an individual rider to visualise the impact of different modifiable factors on fuel use.

If you click the link below, it will take you to the calculator which shows how altering different aspects of diet around a session can influence what fuel source is used. As a cyclist, it would certainly be worth spending 5 minutes playing around with the different variables to see what impact it has on the contribution of different fuels. 

FUEL USE CALCULATOR 

As sports nutritionists, we often hear of riders restricting carbohydrates to try and maximise fat burning during a session, but as you'll see in the calculator the impact of fuelling on fuel use during exercise is relatively small.

If you want to learn more about how best to fuel your rides, then check out Fuel The Ride Academy where we not only give you the science and theory behind why and how to fuel but also provide the practical strategies to implement this and develop your own optimal strategy as well as the individual support to help implement this. Check out more in the links at the top of the page. 

Coach Ben 

Reference 

Rothschild, J. A., Kilding, A. E., Stewart, T., & Plews, D. J. (2022). Factors Influencing Substrate Oxidation During Submaximal Cycling: A Modelling Analysis. Sports medicine (Auckland, N.Z.), 52(11), 2775–2795. https://doi.org/10.1007/s40279-022-01727-7