Carb loading and how to do it properly – with help from HYROX
Written byLiz Connor
Reviewed byEmily Foster
What if one small change could make a big difference on race day? We spoke to a HYROX expert and two nutritionists to find out about the benefits of carb loading
Summary
1What exactly is carb loading?
Carb loading is a nutrition strategy that is designed to improve fitness performance in endurance sports.
2How many carbs should I aim for before an event?
Dr Collins recommends aiming for a diet that delivers eight to 10 grams of carbohydrates per kilogram of bodyweight.
3What should I eat when I’m carb loading?
You could start your morning with jam and peanut butter on a bagel, with a banana and a glass of apple juice (approx. 130g of carbs).
Wondering how to prepare for a marathon, iron-distance triathlon or HYROX race? Just as important as having the right gear (hello, new trainers) is having the right nutrition in the run-up. And that’s where carb loading comes in. This simple nutrition strategy promises to help you run further, lift longer and cycle faster, by making subtle tweaks to your diet in the days and hours leading up to the big day.
To help us understand the how, when and why of carb loading, we asked top sports nutritionist, Dr Adam Collins and HYROX master trainer Jake Dearden to run us through the basics. See you on the starting line…
What exactly is carb loading?
“Carb loading is a nutrition strategy that is designed to improve fitness performance in endurance sports,” says Dr Collins. “In its simplest form, it involves supplying your body with higher amounts of carbohydrates before an event, match or competition.”
“By eating more carbohydrates, you’re essentially adding more petrol to your tank”
The science behind going hard and fast on carbs is pretty simple, he explains: “At a biological level, your body uses the glycogen stored in your muscles to provide the energy needed for exercise. It produces this glycogen by breaking down the carbohydrates you eat. So, by eating more carbohydrates, you’re essentially adding more petrol to the tank and providing your body with the vital energy stores it needs to dig deep during a long-distance effort.” Put another way, more carbs means more fuel.
Don’t just take our word for it though; for decades now, carb loading has been the dietary weapon of choice for elite endurance athletes. Eight-time Olympic Gold sprinter Usain Bolt is known to eat up to 450 grams of carbs a day during intense training periods, while Serena Williams habitually loads up the night before a Grand Slam with carb-dense foods like rice or pasta.
Sadly, it’s not quite as simple as eating a bigger bowl of porridge on race day, however. “Alongside tweaking their diet, athletes tend to dial down their training intensity and volume in the run-up to an event, to help preserve that stored muscle glycogen,” says Dr Collins. So try to moderate your training in the days immediately before.
Can carb loading improve my fitness performance?
“With more glycogen in the engine, athletes find that they can perform at a higher level for much longer, giving them the edge in endurance events where maintaining a good pace can be really challenging in the later miles or stages,” says Jake.
Jake adds that carb loading can help you to avoid hitting total glycogen depletion too. Known in workout circles as ‘bonking’ – or simply ‘hitting a wall’ – it marks the point at which the body’s glycogen stores have run out, making each step towards the finish line torturously difficult.
While carb loading might sound like yet another TikTok buzzword, it has an impressive amount of peer-reviewed scientific research to back up its benefits. One study review1 found that prioritising carbs before an event lasting 90 minutes or more may improve your athletic performance by 2-3%. Encouragingly, the same researchers found that it could also potentially postpone mid-race fatigue by as much as 20% too.
How many carbs should I aim for before an event?
This all depends on your body composition and sport of choice, but as a general rule of thumb, Dr Collins recommends aiming for a diet that delivers eight to 10 grams of carbohydrates per kilogram of bodyweight. So, if you weigh 63 kg (10 stone), in the days leading up to an event you should try to consume around 500-630g of carbohydrates per day.
“Ideally you want to spend the 48 to 72 hours before race day building up your glycogen stores,” Dr Collins advises. In practice, this looks like three carb-based meals with a mid-morning and afternoon snack slotted in between.
But don’t worry if maths isn’t your strong point; nutrition tracking apps can do the hard work for you. MyFitnessPal has a handy log feature that allows you to input your meals and portion sizes so you can monitor your carb intake as you inch closer to the starting gun. Simples.
“Focus on consuming easily digestible, high-carb foods”
What should I eat when I’m carb loading? And will carb loading impact my gut health?
Although fibre is a super important part of a healthy diet, too much can cause gut health issues like bloating and discomfort2 – the sort of stuff that can really affect your race-day mojo. We asked our in-house sports nutritionist Emily Foster for her lowdown on loading up.
"Carb loading is one instance where we recommend steering clear of high-fibre foods like wholegrains and beans as they stay in your digestive tract longer than low-fibre carbohydrates, which might cause digestive problems on race day. Instead, focus on consuming easily digestible, high-carb foods like white bread and white rice over wholegrains and reduce your intake of beans and high-fibre vegetables,” says Emily.
“While carb loading involves increasing your carbohydrates compared to a regular day, it doesn’t mean you should increase your total daily calorie intake too. You’ll need to reduce fat and protein intake to balance the increase in carbohydrates. Reducing fat intake is recommended close to races anyway, as fats are harder to digest and can cause digestive upset.”
Whet your appetite? Emily has some tasty suggestions for counting up those carbs.
“Aim to distribute your carbohydrate intake throughout the day rather than leaving it all until the evening. For example, kickstart your morning with jam and peanut butter spread on a bagel, with a banana and a glass of apple juice (approximately 130g of carbs) or pancakes topped with maple syrup, blueberries, a banana and a glass of orange juice (approximately 119g of carbs). For snacks, white pitta bread with dips or flapjacks are good choices.”
What’s the one thing I need to remember about carb loading?
“Always dry run your carb loading strategy before race day,” stresses Jake. “Everyone’s microbiome is different and the worst thing you can do is eat a food that doesn’t agree with you the day before your race. Experiment with different carb-heavy foods during your training and you’ll be topped up and ready for anything.”
The final say
Carb loading isn’t about overindulging or second-guessing every bite – it’s about fuelling your body with purpose. When done thoughtfully, it can give you the energy, confidence and staying power to show up strong and finish even stronger. Pair it with smart training, a bit of trial and error and an understanding of what works best for your body. You’ll be ready to set yourself up for success long before the starting line.
Looking for more carb loading for a specific sport? Check out our ultimate football nutrition and cycling nutrition guides for more.
Disclaimer – This article provides informational advice and is not a substitute for medical care. Working with experts for accuracy, we take great care to ensure the information is up-to-date and relevant. However, you should always consult your GP or healthcare professional before using supplements or alternative products, particularly if you have medical conditions or are under supervision.
- Hawley JA, Schabort EJ, Noakes TD, Dennis SC. Carbohydrate-loading and exercise performance. An update. Sports medicine (Auckland, NZ) [Internet]. 1997;24(2):73–81. Available from: https://www.ncbi.nlm.nih.gov/pubmed/9291549
- Physiotherapy Service Patient information Fibre General information [Internet]. Available from: https://www.uhd.nhs.uk/uploads/about/docs/our_publications/patient_information_leaflets/physiotherapy/fibre.pdf
