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Avoid the Bonk: Common Race Day Nutrition Mistakes and How to Fix Them
on May 14, 2025
When it comes to endurance performance, your fuelling strategy can be the difference between a strong finish and a race-day meltdown.
To help athletes avoid common nutritional pitfalls, we’ve teamed up with expert performance dietitian Cushla Holdaway, who holds a Master's degree in Sports and Exercise Nutrition and works with elite endurance athletes across New Zealand and beyond.
With years of hands-on experience helping runners, triathletes, and cyclists optimise their fuelling strategies, Cushla (pictured) brings Part 3 of her evidence-based insights and practical advice to help you get it right when it counts.
Preparing for a race isn’t just about training physically, it’s also about preparing your body enough with sufficient and strategic fuelling. Even experienced runners can make simple mistakes that compromise energy, performance and digestion on race day. Here are the most common nutrition pitfalls I see in athletes seeking advice and how to prevent them.
1. Not training your gut at race intensity
Your gastrointestinal system is a muscle and must be ‘trained’ to adapt sufficiently to tolerate certain amounts and types of carbohydrates and fluid volume, especially at race intensity. Many athletes believe what worked in a couple of easy training sessions will translate to working in a tough race, but overloading an untrained gut can lead to a upset tummy, limited fuelling and potentially a dreaded DNF. Practice your nutrition strategy during key training sessions that mimic race day as best you can, focusing on experimenting with different types of fuel sources, the timing, and overall volume of carbs (g) and hydration (mL). This not only fuels your training well (vital!) but builds confidence in your race day plan, and reduces the risk of unwanted tummy troubles when it matters most!
2. Poor aid station preparation
If your race has aid stations (AS) and you plan to rely on them, practising your method of intake is crucial, whether this is grabbing your personal bottles, refilling flasks, or grabbing the cups provided ‘on-the-run.’ Aid stations aren’t always stocked exactly how you need them, so consider having backup options if possible. Preparing ahead prevents delays when time is of the essence, missed fuelling opportunities, and ensures you get more fuel and/or fluid in your mouth than down your front.
3. Overlooking weather and environmental conditions
Weather…whether it is hot, cold, windy, rainy or humid, will impact your fuel and hydration needs, clothing choice, and perceived effort, so adapt your plan accordingly. Altitude is another very important factor to consider (but we can cover this for another blog!)
4. Failing to plan for self-sufficiency (ultras)
In events with large gaps between crew points or AS (e.g., 20 – 30+ km), you need to be self-sufficient. Practice carrying enough food and hydration in training, alongside any compulsory gear, and develop a plan to support yourself unsupported. Can you fit everything you need in your running vest? What is your total fluid carrying capacity and is this enough for your requirements, planned pace, and weather conditions? Have you practised running with your vest completely full in training to know if this is comfortable and where fluid and snacks are most accessible?
5. Forgetting about the ‘dress rehearsals’
Many athletes neglect rehearsing their pre-race fuelling plan (e.g. getting familiar with race day breakfast), especially the timing. How many times have you practised eating your planned race day breakfast at 4am for a 6am run start? Add race-day nerves into the mix and suddenly that breakfast plan could go out the window missing your first crucial fuel opportunity in the day. As I always say, train as you would race!
In summary: Effective race-day nutrition isn’t about quick fixes, it’s about consistent, strategic preparation in training over and over again.
Small adjustments in how you prepare and execute your nutrition plan can significantly influence your performance, helping you finish strong and avoid preventable issues…. And don’t forget the number one rule, nothing new on race day!
Cushla (left) is an Accredited Sports Dietitian based in Mid-Canterbury, specialising in nutrition for endurance athletes from beginners to elites. Cushla is also the dietitian for the New Zealand Defence Force (Burnham), runs online education courses, and hosts a podcast ‘Nourish Your Potential.’
With a BSc in Human Nutrition and a Master of Dietetics (dist), she offers personalised consultations across New Zealand, both in-person and online.
Passionate about running and evidence-based nutrition, she helps athletes optimise performance and health through practical, realistic, and individualised advice.
Catch-up reading in the series so far:
