Even the best laid marathon nutrition plans can go awry with costly mistakes on race day. Some errors might seem minor at first, but can later snowball into significant performance-limiting issues over the course of 26.2 miles.
To help you avoid hitting ‘the wall’ or ending up in the portaloo too often during your next marathon, I’ve taken a look at how you can overcome some common (and potentially race-ruining) fueling mistakes…
1. Fail to train your gut
I see many runners nail their long runs in training without fueling at all, assuming they’ll just take some gels to boost their performance on race day. Others might practice taking carbs in training, but never at race pace, which doesn’t adequately prepare the gut for digesting fuel under race conditions.
Training your gut isn’t just about tolerating carbohydrates. Drinking while running is a skill in itself. Taking fuel without any fluids could also be a recipe for stomach upset, bloating, and poor carb absorption on race day.
Case Study: Lucy Reid’s Tough Lesson
During her debut marathon in Malaga at the end of 2024, Lucy found this out the hard way. She had no issues taking gels in training, but had never practiced drinking at race pace. After a few drinks stations on race day, she began to feel bloated and each sip was causing nausea, which made it harder to fuel effectively.
Case Study: How CJ Albertson Trains His Gut
CJ Albertson built up his tolerance to carbs over time, and now incorporates fueling and hydration into both long runs and speed sessions, regularly taking in 90-100g per hour.
To practice bottle pickups, he loops past his car every few miles, mimicking marathon conditions. This trains his stomach to handle high-carb intakes at race intensity, which paid off as he successfully averaged ~100g per hour when finishing runner-up at the 2024 California International Marathon with no GI discomfort.
How to train your gut: A structured gut training plan should begin 8-10 weeks before race day, gradually increasing your hourly carbohydrate and fluid intake to reach your race-day targets. The last few long runs should essentially be race simulations of your entire nutrition strategy.
Recommended reading: How to train your gut to consume more carb
2. Underfueling (and hitting ‘the wall’)
Carb-loading before races is a great strategy to use, but this alone won’t carry you through your entire marathon. Your glycogen stores will deplete during high intensity exercise that lasts longer than 90-120 minutes, so you’ll need some extra energy mid-race to maintain your marathon pace (i.e. by eating gels, chews, bars, real good, or drinking a carb drink). If you wait until you’re hungry before taking anything, it’s too late. This is when energy levels nosedive, your legs feel like bricks and your goal pace will disappear up the road.
When Kelvin Kiptum shattered the marathon world record with his time of 2:00:35 in 2023, he actually sped up in the final 10km, running his fastest 5km split between 30-35km. This wouldn't have been possible without aggressive fueling throughout the race, ensuring his glycogen levels never crashed, and he could attack the final miles rather than survive them.
A Nike Sports Research Lab study modelled the predicted requirements to run a sub-2 hour marathon for both males and females. Their results recommended that males would need to consume ~93g per hour on average, and females even more at ~108g/h to complete the feat. Why did the study report that women needed more exogenous carbohydrates I hear you ask? Mainly because on average, women have less muscle mass than their male counterparts which means they start with less glycogen both in their muscles and liver. Even if you’re not gunning for a world record, the lesson holds: fueling early and often is non-negotiable.
How to avoid ‘the wall’: Start fueling early. Take your first gel, chew, or carb drink within the first 30 minutes of starting the race. Keep fueling consistently so you don’t reach the point of no return.
Recommended reading: What happens when you bonk?
3. Under- or over-drinking
Hydration is just as crucial as fueling. Even mild dehydration can increase heart rate, core temperature, and perceived effort, making race pace feel harder. As fluid levels drop, the body redirects blood flow away from the digestive system, which can lead to stomach distress (this issue is often mistakenly attributed to a fueling issue, when dehydration is actually the cause).
We’ve worked with athletes who complain of suffering with GI discomfort and muscle cramps towards the end of their marathons. Whilst there are several possible causes of both GI discomfort and cramps, it’s possible that dehydration plays some role in both of these marathon-ruining issues.
On the flip side, drinking too much fluid, especially without electrolytes, can dilute blood sodium levels, leading to a condition called hyponatremia. Symptoms range from bloating and nausea to confusion and, in severe cases, collapse.
Runners who follow rigid hydration schedules by drinking a set amount per hour without considering their sweat rate or thirst response are at greater risk. Slower runners, who spend more time on the course (and therefore have more opportunities to drink at aid stations) are also vulnerable.
To prevent overhydration:
- Consider hydration as a balancing act between fluid and electrolytes
- Use electrolyte drinks to replace sodium lost in sweat
- Measure your sweat rate during long training runs. If you gain weight during a run, you’re probably drinking too much
Both underhydration and overhydration can lead to performance declines. Balancing intake based on individual sweat rates and sweat sodium concentrations is key to avoiding both extremes.
How to optimise your fluid and sodium intake:
- Measure your sweat rate (i.e. how much fluid you lose in different conditions) to dial in how much fluid you need to drink to maintain performance
- Get a Sweat Test to understand how much sodium you lose in your sweat (or look out for the signs that you’re a salty sweater)
Recommended reading: Why sodium is crucial to athletes performing at their best
4. Don’t have an aid station strategy
Elite marathoners usually have the luxury of picking up their personal bottles roughly every 5km (~3.1 miles), making it easier to meet their fueling and hydration needs without carrying anything from the start. To facilitate running at such high speeds, elite runners do typically require a greater amount of carbohydrate and fluid to sustain their elevated outputs. For non-elite runners relying on standard aid stations, a lack of preparation can lead to missed opportunities to fuel and hydrate effectively.
Many runners make the mistake of not knowing where aid stations are located, leading to a panic when they realise they've run past one without grabbing anything. Others don’t anticipate the congestion at early aid stations, which can slow them down or cause them to miss their nutrition altogether.
How to optimise your aid station approach:
- Aim for the second half of each aid station, where fewer runners typically gather, making it easier to grab a drink without breaking stride
- Know what’s available at aid stations, and how often you’ll pass them at your target pace
- Make eye contact with the volunteer cup holder and even point towards them to make sure they know you’re aiming for them
- Slow down a bit if you need to, a few seconds here could save you minutes later
- Be present and aware - everyone is aiming for the same thing so watch out for other runners making sudden movements ahead of you
- Consider starting the marathon with a Soft Flask with your own hydration. Being self-sufficient reduces risk and means you can avoid the early congestion of the first few aid stations
A little preparation can make a big difference in ensuring you get the fluids and fuel you need.
Recommended reading: 4 tips for mastering water stations at a marathon
5. Poor pacing
A common mistake is for marathon runners to go out a bit too ‘hot’ in a bid to ‘bank’ a few extra seconds early in the race. The temptation to go out fast in the early miles is strong, especially when the adrenaline is high, the crowds are cheering, and goal pace feels effortless. But the reality is that “banking time” in the first half almost always backfires.
Renowned coach Mario Fraiolo (2:27 marathoner and host of The Morning Shakeout podcast summed it up well:
In all my 19 years of coaching, I’ve lost count of the number of athletes telling me they wished they’d gone out slower. Funnily enough, I can’t think of a single one who said they wished they went out faster!
A good fueling and hydration strategy won’t save a poorly paced race. If you burn through energy too early, no amount of gels or fluids will bring you back to full strength. Pacing, fueling, and hydration must all work together to maximise performance.
Aim for a negative split: The best approach is to stick to your planned goal pace, even if it feels too easy early on. A well-executed pacing strategy will help you stick to your fueling plan, helping you finish strong rather than fade in the final miles.
Recommended reading: How to pace your perfect marathon
What next?
Marathon fueling and hydration mistakes are common, but they can be avoided with the right approach. Training your gut, fueling early, balancing hydration, planning for aid stations, and pacing properly all work together to ensure a strong race-day performance.
By practicing your strategy in training and making small adjustments based on your needs, you’ll be better placed to perform at your best.
Need help working out much carb, sodium and fluid you should be aiming to consume during your marathon? Use the Fuel & Hydration Planner…
If you’ve suffered any of the common fueling mistakes or you have questions about your strategy, you can chat to one of our Athlete Support Team - Book a free one-to-one video consultation.
