Fitness & Nutrition

Beginner’s guide: understanding energy use in cycling

We uncover the key rules of energy supply and use in cycling so you can make informed decisions about your nutrition intake

Have you ever walked into a café and spotted a group of cyclists huddled around a table, merrily chatting away and chowing down on cake, flapjack, sandwiches, energy bars, coffee and, perhaps in the summer, ice creams? Well, I have. And then, you notice how waif thin they all are, and something just doesn’t add up.

Let’s be honest, the rule of thumb in life dictates that the more you eat, the more you’re likely to put weight on. However, when it comes to cycling, that’s not always the case.

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Such are the energy requirements in order to spend hours in the saddle riding bikes, cyclists often have to consume far more than ordinary people in order to simply be able to fuel the ride and their recovery.

General wisdom dictates that although we have recommended daily allowances for food groups and intakes of carbohydrates, fats, protein and so on, these recommendations are based on an average, assuming a relatively sedentary lifestyle – 2,500 calories for men, and 2,000 for women.

The energy demands of cyclists mean they often need to consume far more than the average person (Pic: Cadence Performance)

As a result, if we take as read that individuals’ base requirements can vary by a great deal outside of these markers, before you add in the extra energy requirements of riding your bike for an extended period of time, these recommendations can become largely meaningless.

It means nutrition requirements tend to be specific to the individual, and as we discover, specific to the kind of riding you do as well. We got in touch with Matt Hart, managing director of Torq Fitness to get some answers to common questions that will help you understand the basic rules and processes of energy use in cycling.

What fuel does my body use?

Put simply, the type of fuel your body uses depends on the intensity of exercise that you’re working at. At low intensities, most of your energy will come from fat.

“If you’re sitting down watching TV, for example, your body burns almost 100 per cent fat as your energy source, and then as exercise intensity increases from there, you start to burn a higher percentage of carbohydrate,” says Hart.

“Conversely, when you’re exercising at a higher intensity, the amount of calories burnt from carbohydrate starts to outstrip those burnt from fat. Then, during very high intensity exercise (where you might be flat out sprinting for ten seconds, for example), we use an instant fuel supply called phosphor-creatine.”

When you’re exercising at a higher intensity, the amount of calories burnt from carbohydrate starts to outstrip those burnt from fat (Pic: Sirotti)

How much energy does carbohydrate, protein and fat give me?

Thankfully this has a simple answer. Taking carbohydrates, protein and far, the three major food types of food required in large amount in any diet, known as macronutrients, you get the following calories (a unit of energy) per one gram:

Carbohydrate = 4 calories per gram

Protein = 4 calories per gram

Fat = 9 calories per gram

How does this convert into energy?

Carbohydrates are stored in the muscles and liver as glycogen, which is then converted into glucose, the body’s preferred energy medium. It’s here that your school biology lessons may start to ring some bells – no doubt a happier experience for some than others – but don’t worry, it’s not as complicated as it sounds.

“Glucose goes through a process called ‘glycolysis’, a process which releases some energy for immediate use, and over a number of steps becomes something called ‘pyruvate’,” says Hart.

“This pyruvate is useful as it can then get turned rapidly into lactic acid for an instant anaerobic energy supply – useful for sprints or a short hard effort.

“It can also be used in a process called the ‘Krebs Cycle’, where it’s burned along with fat in the presence of oxygen (aerobic) to produce lots of energy.

“Basically, glucose can be used to either raise energy quickly via the anaerobic route, but you need a lot of it, or it can be burned aerobically with oxygen and fat. This has a slower turn-around but uses much less glucose from your stores.”

Protein is more commonly used in recovery but can be used for energy, too (Pic:

What about protein for energy?

Protein is generally the building block for the body’s repair and growth systems, but yes, it can also be used for energy.

Hart says that to release the energy from protein, it has to undergo an energy-costing process called ‘gluconeogenesis’ – quite literally meaning ‘new creation of glucose’ – where it is converted into glucose.

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However, Hart has a warning: “Forcing your body to glean energy from protein by restricting carbohydrate intake doesn’t hold much logic, because once readily available, ingested protein has been used up, and your body will scavenge for it from your lean muscle mass.”

How do cycling intensity and duration affect my energy requirements?

The kind of riding you do will affect your energy requirements markedly and should be considered carefully when thinking about your energy intake.

Consider the two examples below:

  • Short duration, intense riding (e.g. crits, time trials, turbo sessions)

“Crits tend to be very much on and off the gas over a relatively short duration (about an hour) so you’re effectively having an interval session,” says Hart.

“The part you play in the race will determine energy usage and fuel utilisation, because if you’re strong enough to spend a lot of time on the front dragging the rest of the peloton along, you’ll be sitting at an intensity called ‘FTP’ or ‘Anaerobic Threshold’ where you’ll be burning a decent percentage of fat as well as carbohydrate.”

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As Hart explains, the problem with this is that you’ll be ripping through your stored carbohydrate at a great rate while riding at this intensity.

“However, if you’re the kind of person who sits in the bunch and spends the race responding to attacks, or making a few yourself, the intermittent nature of the racing will mean exceptionally high carbohydrate burn rates whilst going full gas. Then, when you’re drifting in the peloton, you switch more towards using fat, because the intensity is lower,” he says.

Stored carbohydrate is used at a greater rate during intense efforts, whereas fat is burned if the effort is more steadier and more consistent (Pic: Sirotti)
  • Long, steady rides

Conversely, long steady rides tend to encourage a greater proportion of metabolising fat. Of course, there will likely be moments when you switch to harvesting carbohydrates, perhaps on a climb when the intensity rises, but for the majority of your time you may be ticking along, happily riding socially or in a group, for example.

“The fact that these rides are lower in intensity and don’t incorporate too many changes of pace means that your body can easily utilize oxygen and fat as reliable fuel sources,” Hart says. “Any sudden change of pace during these rides however will be met by carbohydrate, because the energy will need to come from anaerobic sources.”

I’ve heard that I burn even more calories after my rides – is this true?

Yes, the activity of cycling also causes a greater utilization of energy when you’re recovering too. Hart explains that there are two main reasons for this.

“Firstly, if you’ve had a challenging ride, you will have caused damage to your muscles and created a trough of fatigue, so your body will elevate your metabolism because it has work to do in re-building you,” he says.

Energy continues to be used during the recovery process (Pic: Sirotti)

“Secondly, muscle is a living tissue, which requires energy to simply exist, so this new living tissue has an energy requirement at rest just to stay alive.

“People who train regularly have more lean muscle mass and hence a higher resting metabolic rate, which should help you utilise more fat for energy while resting.”

I run out of energy more quickly than my friends – why could this be?

We all have individual energy needs when it comes to fuelling our bodies. In day-to-day life, a sedentary person may need as little as 1,200 calories to maintain energy levels and body composition, while a different person with a similar lifestyle may need twice this amount, perhaps more.

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Exercise adds to this energy need, while other factors such as the body’s natural and trained abilities to metabolise certain kinds of fuel, as well as its ability to efficiently use fuel (among a host of other considerations) make up your total energy need.

It’s therefore impossible to prescribe exact amounts of carbohydrates blindly to individuals (so, if you’re spending time looking online and reading articles for exact recommendations for you, you can stop now safe in the knowledge that catch-all recommendations exist), but Hart says that there are certain guidelines that you can follow and experiment with to find your optimum energy fuelling strategy.

“The key to successful fuelling is to start the process from the moment you start cycling,” he explains. “Every gel, bar or swig of energy drink you have gives your body carbohydrate that it can burn readily, instead of using stored carbohydrate, of which you can store around 2,000 calories worth. We call this ‘glycogen sparing’.

“The more glycogen you can spare, the longer you’re going to last and the faster you can afford to ride without worrying about running out of energy.”

Logically, therefore, the more carbohydrate we can consume per hour, the more pronounced this effect will be, although there are limits. Hart points out that not all energy products are the same, with some sticking with using mainly glucose derivatives, which he claims is an outdated approach, because absorption in the body is limited to 60 grams per hour.

“All of the modern research is pointing towards a formulation of 2:1 glucose and fructose because it allows dual transport of two different types of carbohydrate into the blood, leading to 90 grams of absorption per hour,” he says.

Food intake on and off the bike should be considered (Pic: Chapeau)

Where can I get a balanced energy intake from?

 You need to look at this in two ways, according to Hart – your nutrition off the bike, as well as what you consume on the bike.

“Firstly, your general diet needs to be balanced and healthy with a mixture of healthy nutrients,” Hart says. “You should be ensuring that you consume at least 20 grams of protein every few hours and your carbohydrate intake needs to match your training volume and intensity.

“The more energy you use, the more carbohydrate you should aim to consume so that you keep your essential glycogen stores [for everyday living and recovery] topped up.”

Secondly, you need to look at your nutrition while riding, remembering that if you fuel properly on the bike you will conserve your stored glycogen for when absolutely necessary, meaning you will be able to ride harder or for longer.

“The flip side of this is that your glycogen stores will be less depleted at the end of the ride, so you’ll be less tired and will have less recovering to do,” Hart also points out.

An energy bar or gel will give you a ‘pick me up’ but if you’re already short of energy when you take it, it’s too late (Pic: Allan McKenzie/

The chances are that you’re familiar with the different forms of convenient nutrition products, including energy drinks, bars and gels.

However you decide to fuel yourself, remember that the big mistake some riders make is that they let their energy reserves run out and then decide to take a gel or eat an energy bar.

Hart says that although this will provide an immediate ‘pick me up’, your pace will be significantly lower than if you’d retained your stored carbohydrate. Ultimately, you will only be able to work as hard as that product allows because your requirement for carbohydrate at high intensity vastly outstrips how quickly you can supply it.

“We have a motto, which is ‘eat today for tomorrow’,” says Hart.

“It’s great advice because it means having a clean healthy diet on the one hand, and structuring your nutrition so that – if you know you’ve got a run of tough sessions coming up with little recovery between them – you can get ‘on it’ with the nutrition and fuel the earlier sessions.

“That way, you’re not under-performing midway through the tough section of your training block.”

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