Four nutrition myths that every ultra-runner needs to know

Whether you want to set a new personal record at your next ultra-marathon, increase your running distance, or improve your health, you've likely taken a stab at tweaking your diet or nutrition strategy.  

Unfortunately, there's a lot of nutrition advice out there that won't help you meet your goals and could actually do more harm than good.

So, in this post, I’m debunking four myths to help you get on the right track for good. 

Nutrition Myth #1: You need to lose weight to run faster

Years ago, the idea that losing weight would help runners move faster was widely accepted. After all, if you were lighter, you’d be quicker on your feet—right?

At least we all thought it worked, and its logic made good sense. That’s why trying to get as light as possible in the lead-up to a race became so popular. 

However, pursuing this objective isn’t as beneficial as we used to believe. 

The main reason? 

To drop weight ahead of your race, you must restrict your calorie intake. Calories are energy for your body, and when training for an ultra, your body needs lots of them. 

Another important reason is that most weight loss expectations are based on pure math without accounting for physiology. Energy restriction raises a big red flag for your body, triggering defence mechanisms. You’re always hungry, struggle to recover from training, and your overall performance hits a wall. 

There are other reasons, too. Reducing your energy intake increases your risk of injury, slows down recovery, and ultimately hinders performance.

This means that to reach your peak performance, focusing on losing weight only steers you in the opposite direction of your goals. 

What to do instead

You need to fuel your body right for optimal performance. In fact, a recent study compared a weight loss intervention against a regular fuelling intervention among race walkers and the results were astonishing. Not only was the performance of the weight loss group not better than that of the control group, but participants also experienced increased fatigue, stress, and decreased recovery. 

So, if you’re looking to make it to race day strong and prepared, here’s the approach I recommend trying out.

1. Set a different objective. What is your ultimate outcome? What do you want your race to look like? Work on that instead. 
2. Use other metrics to track your progress. Ditch the scale and monitor your progress using metrics that actually measure your fitness, such as your average heart rate, running pace, power, perceived effort and recovery. 
3. Use food as fuel. Calories are energy, and your body needs them. 
4. Work with your body, not against it. Rather than restricting your energy intake, focus on what is missing in your diet to support your optimal nourishment. 
5. Use nutrition strategically. There’s so much more to nutrition beyond counting macros and calories. Being deliberate about your fuel choices and timing can make a massive difference to your performance and race day success.   

Nutrition Myth #2: Fasted training is ideal for becoming fat-adapted

While fat-adaptation is important, completing all your morning runs without any food in your stomach is futile. 

You are heading into training with minimal energy, and the quality of your training session is compromised. 

And if that’s not enough, here are three other reasons fasted training won’t work:

• Reason #1: You’re putting your body under significant stress. Your body needs to pull energy from somewhere, and yes, a lot of that will be coming from your fat stores but also from your glycogen, and if there’s not much in the tank, sustaining the effort at the pace you’re expecting will be almost impossible. 
• Reason #2: The likelihood of experiencing gut issues on race day increases dramatically. It will be difficult for your digestive tract to process and absorb fuel if this is something that you rarely try during training. 
• Reason #3: Plus, you won’t be able to stop thinking of food for the rest of the day. As I mentioned above, your body is very clever. Your body sees your fat stores as your savings. You took out a big loan during your fasted training, and your body will soon ask for payment.

What to do instead 

Fuelling before your training sessions will help you improve the quality of your training, support your recovery and reduce the likelihood of gut issues sabotaging your race. Combine this with fuelling during runs longer than 90 minutes, and you’ll be ready to fuel your best performance. 

The best part is that it’s been shown that even after consuming a good meal, your body still uses a significant amount of fat as fuel, which means training itself will ultimately increase your fat adaptation despite your nutrition.

Nutrition Myth #3: Gut issues are just part of the race

One of the most persistent myths about ultra-running is the idea that gut issues are just something you have to deal with during long races. Many athletes believe that nausea, diarrhea, or bloating are simply part of the experience, especially in endurance events where your body is under extreme stress.

But this is not true! Gut issues do not have to be part of your race day struggle, and accepting them as inevitable could be holding you back from achieving your full potential.

Gut problems can often be traced back to poor nutrition strategies, such as relying on too much fibre, improper hydration, or untested fuelling options. While gut issues might have been common when athletes weren’t aware of these factors, we now know they can be managed or completely avoided with the right approach.

What to do instead

Instead of accepting gut issues as part of the race, optimise your nutrition strategy to avoid them altogether. This means focusing on:

• Reducing fibre intake in the days leading up to your race.
• Testing all your fuel options during training so you know what works for your body.
• Checking for intolerances that could be causing discomfort, like lactose or certain sports drinks.
• Training your gut to absorb fuel more efficiently over time.

For example, my client Sophie struggled with gut issues for years during long runs and races until she followed the fuelling tools and gut prevention strategies I share inside the Fuel To Thrive Academy. Sophie developed a tailored fueling plan that allowed her to stay energised, eat frequently, and eliminate gut issues during her last 100 km race at UTA.

Nutrition Myth #4: Nutrition only matters on race day

The truth? Focusing solely on race-day fueling won’t cut it for achieving peak performance.

Even though having a race-day nutrition strategy is fundamental, focusing on just that day won’t get you the results you’re aiming for. The problem is that your body requires consistent fueling during training to build up the endurance, energy reserves, and adaptations necessary to excel on race day.

To get the results you want, you should be fuelling properly during race preparation, not just on race day. Consistent fuelling is vital to building a strong body that can perform at its best when it counts.

Take the Tour de France as an example. Cyclists have now expanded their focus beyond what they eat during the race—they fuel deliberately throughout their training preparation, building up their endurance and strength over time. This is one of the main reasons we saw unparalleled results this year, with many participants breaking long-held course records.

World-leading expert and my former Professor, Asker Jeukendrup, even states that nutrition can significantly impact training adaptations and is an essential tool to optimise performance effects. It is not just the muscle that is affected; other tissues, such as the brain, the vasculature and the intestine, can also be affected.

Client Case Study: Len's Success

Previously, during Ironman events, Len faced issues with hydration and fuelling, resulting in subpar performances, particularly during the run leg. 

Through our work together, we uncovered that he wasn’t fuelling his training sessions well enough and wasn’t practising his fueling strategy during training to condition his stomach for the required amount of carbohydrates. Through a sweat test, we also discovered that his fluid and salt losses were much higher than average.

Len shares, “Gaby was great at explaining how these things impact my performance, and it was a surprise to find out exactly how much carbohydrate and fluids it takes to successfully fuel Ironman training & racing. We worked on my nutrition plan weekly, allowing my body to get used to the amount of carbs it was taking on board. This enabled one of the best training blocks I’ve completed and set me up for a great race in Cairns, where I had a strong run and PB'd by over 10 minutes on a challenging course.”

What to do instead

Instead of waiting for race day to focus on your nutrition, start making deliberate food choices during your training preparation. This approach will allow your body to adapt more efficiently, giving you the endurance and energy you need for training and race day.

A simple step you can take today is to start incorporating a post-training recovery meal or snack rich in carbohydrates and protein, ensuring that you have the nutrition to support your post-training recovery.

This is effective because it ensures your body has the fuel to maximise the physiological adaptations from your training, ultimately leading to improved performance when it matters most.

Wrapping it Up

There you have it: 4 ultra-running nutrition myths. 

As you saw, nutrition for ultra-endurance is evolving, and you should be, too. Today, it’s more about fuelling with purpose and not restricting energy or relying on outdated strategies.

I hope this post has helped you steer clear of misleading information so you can start fuelling your race day success.  

Now, over to you. Which of these myths did you find most surprising?