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She Runs Outdoors

Fuelling Strategies for Ultra Marathons: A Conversation with Dietitian Alex Cook BSc (Hons) Pg. Dip. RD

As an ultra running coach, I often find when I start working with an athlete, they have often found the race, thought about training plans and maybe even kit, but overlooked a crucial component: ultra marathon nutrition. Whether you're gearing up for a challenging trail race or a gruelling ultra, your diet plays a pivotal role in performance, recovery and overall health. A lot of athletes don’t even start thinking about their fuelling until the race is just around the corner.

This time of year, many of the women on the She Runs Outdoors team are starting to focus on training for summer ultras. From the get-go, I’m getting them to think about fuelling. Fuelling is so personal, and it can take a little time to find your sweet spot, likes/dislikes. Practicing it throughout your training gives you time to experiment, and as you up your training, it’s crucial to be aware of how much you need to support the level of training. Having good nutrition overall is smart and key to longevity in our sport.

In the world of social media and the internet, there can be a lot of confusing advice about diet and fuelling for endurance. Within my coaching practice, my go-to person for expert advice or to signpost my athletes to if they need support beyond my scope of practice is seasoned sports dietitian, fellow Salomon Ambassador, and my good friend Alex Cook.

Sports Dietician Alex Cook and Trail Ultra running Coach Rachel Murphy discuss fuelling ultra marathons
Salomon Ambassadors, Sports Dietician and England Athletics Coach Alex Cook and UESCA Ultra Running & England Athletics Fell and Mountain Running Coach Rachel Murphy

Photo by Oliver Denton-Salomon

The Sports Dietitian Alex Cook runs a specialised consultancy catering to the nuanced needs of athletes, particularly in endurance sports and eating disorders. With a robust background spanning 18 years as a sports dietitian within the NHS, Alex brings a wealth of expertise to the table. But her involvement doesn't stop there; she's deeply entrenched in the athletic world as a UKA athletics coach and her work with Salomon.

What sets Alex apart is her firsthand experience as a competitive distance runner, amassing two decades of personal journey in the field. This unique perspective enables her to offer practical, realistic advice, grounded in her own experience as an endurance athlete and her education. She has a BSc (Hons) in Sports & Exercise Science from the University of Birmingham and a postgraduate in Nutrition & Dietetics.

Back when I first met Alex many years ago, she changed the way I approached my race nutrition. It’s advice I have always been grateful for as it changed my experience and helped me fine-tune my race fuelling, allowing me to race better and recover well after doing so. I recently caught up with Alex to chat about trail running fuelling stratergies and sports nutrition for long distance runners and endurance athletes.

The Importance of Fuelling for Ultra-Distance Events

Rachel: Alex, why is it so crucial to have a fuelling strategy for ultra marathons?

Alex: Training and racing for an ultra is tough. It's not just about running; it's also about planning. You need a strategy for how you will tackle the distance and how you will fuel it. The main aim is to maintain a high energy output over a long time. Energy expenditure is extensive, so you must pay close attention to your nutrition plan, just as you do your training schedule, to make the most of your efforts.

Rachel: Absolutely. I often see runners focus heavily on their training plans but neglect their nutrition, which can be a game-changer in performance and recovery. I also think that sometimes people can need help to plan for much longer events to account for more challenging terrain than they have had to consider previously.

Basic Daily Nutrition

Rachel: What are the first steps runners should take in their daily nutrition?

Alex: The first aim is to get your basic, day-to-day nutrition right. Keeping a food diary can help identify gaps in your diet. Ask yourself questions like: Am I eating three meals a day? Am I eating a balance of food groups at each meal? Am I drinking enough water? Am I eating five to seven portions of fruit and vegetables a day? Focus on one thing at a time, such as drinking more water or having breakfast every day and be consistent with that change.

daily nutrition for endurance runners

Rachel: From a coaching perspective, I always stress the importance of consistency. Just like in training, small, consistent changes in nutrition can lead to significant improvements over time. I work with women who have very busy lives so they often have me checking in, to make sure they aren’t so busy they are skipping meals because along with getting enough sleep and rest, what we do around our running really has a big impact on our performance

Meeting Energy and Nutrient Demands

Rachel: How should runners address their energy and nutrient demands during training?

Alex: As training volume increases, so does the demand for energy. Carbohydrates are the main source of fuel, and runners should aim for approximately 5-7g of carbohydrate per kg of body weight. Protein is also essential for muscle repair and adaptation, with an aim of 1.2-1.8g per kg of body weight per day. Ensure you have a portion of protein at each meal.

Meeting Energy and Nutrient Demands, carbohydrates and protein

Pre- and Post-Training Nutrition

Rachel: What should runners consider for pre- and post-training nutrition?

Alex: For pre-training, have a carbohydrate-rich meal with moderate amounts of protein and fat 2-4 hours before your run. Post-training, focus on the '3 Rs of Recovery': Rehydrate with water or an electrolyte drink, refuel with carbohydrates, and rebuild with protein. Aim to consume these within an hour of finishing your training.

woman preparing food

The '3 Rs of Recovery':

  1. Rehydrate: Drink 500ml fluid immediately after your run, then little and often until your urine is clear or you have reached your pre-run weight.

  2. Refuel: Ensure you’re eating enough carbohydrates within a well-balanced snack or meal within an hour of finishing exercise.

  3. Rebuild: Get into the habit of having approximately 20g of protein within your post-training snack or meal, and then regularly at each meal and snack for the remainder of the day.

Rachel: You really helped me with this personally. I’m forever quoting you with my athletes. I agree, timing is so important. I remind my athletes to have easy to prepare, post run options in the house or their car. Taking full advantage of their freezer and plan their meals and snacks around their training sessions to maximise energy availability and recovery. Because we all know as training volume goes up we often don’t feel like going to lots of effort to make things!

Race Day Fuelling Strategy

Rachel: What is your advice for fuelling during an ultra marathon?

Alex: Start fuelling early, around 20-30 minutes into the race, to keep your energy levels up. Aim for 60-90g of carbohydrates per hour. The form of carbohydrates can vary – gels, energy chews, sports drinks, or real food, depending on personal preference and tolerance. It's also crucial to stay hydrated but flexible with fluid intake based on individual needs and race conditions.

The “Gold Standard” for carbohydrate consumption during exercise is approximately 60g per hour with a maximum possible absorption of 90g/hour if taken in a 2:1 blend of glucose (known as dual carbs). This combination increases absorption rate over time, resulting in very high oxidation rates.

Practical top tips:

  1. The science provides the guidelines but be flexible, as no matter what the science says, you are more constrained on the day by what your stomach dictates.

  2. Find out what products are available on the course/checkpoints, training with them may mean you can rely more on checkpoint nutrition.

  3. Use your long training runs to conduct experiments on how much and what type of fuel you can tolerate.

  4. If new to taking on carbs during running, start with 20-30g carbohydrate per hour, little and often of either single or dual source carbs and aim to work up to 60g/hr.

  5. Remember to reach 90g/hr you need to be using only “dual” source carbs to reach this amount.

  6. Set your watch to bleep every 20-30 mins to remind you to fuel.

  7. Start fuelling early whilst the gut is fresh and absorbs carbs easily, things might not be so easy a few hours into the race!

Rachel: Yes, It’s important to train your gut just as you train your legs. I’m always reminding the women I coach to practice race day nutrition strategy during long training runs to see what works best for them to avoid any surprises on race day. Fuelling is so personal, both how much and what we like so try lots of different things, work out which products and flavours you like. Giving yourself options can save the day when you have taste fatigue or something you used in training isn’t agreeing with you. The starting early was a game changer for me when you first told me to do it Alex. I advise people to have a little post long run audit of how many carbs per hour they had by counting up their empty gel wrappers and noting down any extras and write down how they felt. This helps work out their sweet spot and avoid them suddenly jumping up how many carbs they use on race day beyond what they have trained with. I help my athetes plan how long we estimate their race will take so we can plan their race day nutrition needs, working out what they will take with them and what is available at aid stations.


Fuelling for ultra marathons requires careful planning and consistent practice. By combining expert nutritional advice with practical coaching tips, you can optimise your performance and recovery. Remember, nutrition is highly individual, so take the time to find what works best for you and stick to it.

She Runs Outdoors coach, Rachel Murphy GB Ultras Pennine Barrier 3rd Female

Photo Ridgeline media/ Pennine Barrier GB Ultras

Find out more from Alex: The Sports Dietician Website

contact Alex Cook sports dietician



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