You may have heard of training your body to run further or faster, maybe even training your brain for the mental challenges that runners can face. But have you ever heard of training your gut?

It’s a huge part of marathon or long-distance training, but is all too frequently overlooked. Ensuring that you know what and when to eat can significantly improve your performance on race day, so it’s really important to train your gut in the weeks leading up to the race.

Marathon runners are famously committed. They follow structured training plans, log long miles, complete strength sessions, schedule recovery, and nail pacing workouts. Yet despite all this preparation, race day can still unravel. Not because of the legs. Not because of the lungs. But because of the gut.

Your digestive system is a muscle like any other, and it needs training just as much as your heart, lungs, legs, and mind. Whether you’re training for your first marathon or chasing a personal best, a structured and personalised nutrition plan is essential.

The Role of Nutrition in Marathon Training

Clemence Cleave, Nutritionist at Pure Sports Medicine, explains, “Race-day fuelling gets a lot of attention, but marathon performance is built over months. Focusing on a balanced daily diet is the foundation that supports training load, resilience and recovery.”

Nutrition is the backbone of any successful marathon training programme. Nausea and “hitting the wall” are common conditions marathon runners experience, which can be avoided through training your gut while you run. As an endurance athlete, your body demands a precise balance of nutrients to fuel long runs, facilitate recovery, and support overall health. Proper nutrition not only enhances performance but also reduces the risk of injury and accelerates recovery time. As you embark on your marathon journey, understanding the role of nutrition can make a significant difference in achieving your goals.

Incorporating a well-rounded diet with a focus on carbohydrates, proteins, and fats is essential. Carbohydrates provide the primary energy source for your muscles, while proteins are crucial for muscle repair and growth. Meanwhile, healthy fats contribute to sustained energy levels during longer runs. By integrating these nutrients into your daily meals, you can optimise your training results and maintain peak performance. Even more important is to train with the foods that you want to use on race day, just as you would do your run training, your gut equally needs to be trained.

Understanding Caloric Needs for Endurance Athletes

Endurance athletes require a higher caloric intake compared to the average person due to the increased energy demands of their training. Understanding your specific caloric needs is vital for maintaining energy levels and preventing fatigue. The number of calories you need depends on several factors, including your age, gender, weight, and the intensity and duration of your workouts.

To calculate your caloric needs, consider using the Harris-Benedict equation or other reliable metabolic calculators. These tools consider your basal metabolic rate (BMR) and activity level to estimate your daily caloric requirements. Once you know your baseline, you can adjust your intake based on your training schedule, ensuring you’re consuming enough to fuel your runs and recover effectively.

Although these tools are useful, even more important is to consider fatigue during and after your training, as well as your hunger – how your body feels. Learning to recognise how your body feels and adjusting will be optimal in being on top of your nutritional needs.

Strategies for Balancing Calories Burned with Calories Consumed

Balancing calories burned with calories consumed is a crucial aspect of marathon training. To achieve this balance, it’s important to monitor both your energy expenditure and dietary intake closely.

Start by tracking your workouts, documenting the distance, duration, and intensity of each session. This information will help you estimate the calories burned during training. A practical way to do this is using The Rate of Perceived Exertion (RPE) scale for your workouts, which monitors how hard you found the session, and to reflect on your sessions if you feel next time you should have had more water/fuel or if what you did was well balanced.

Simultaneously, keep a food diary to record your daily intake, focusing on portion sizes and nutrient content. Aim to replenish the calories burned during a run with nutrient-rich foods that support recovery and performance. Consider eating small, frequent meals throughout the day to maintain energy levels and prevent overeating. Listening to your body’s hunger cues can also guide you in managing calorie intake effectively.

The Impact of Proper Hydration on Recovery

Hydration plays a vital role in both performance and recovery during marathon training. Adequate fluid intake supports cardiovascular function, regulates body temperature, and aids in nutrient transport to your muscles. Dehydration, on the other hand, can lead to decreased performance, increased fatigue, and a longer recovery period.

It is also important not to overhydrate, as this can increase your risk of developing hypernatremia, which is even more serious. A way to do so is by drinking when you’re thirsty, ensuring it is regular and often, and making sure not to wait until you are very thirsty.

To ensure proper hydration, aim to drink water consistently throughout the day, not just during workouts. Consider carrying a water bottle with you to remind yourself to sip regularly. During longer runs, incorporate electrolyte-rich sports drinks to replace lost minerals and maintain fluid balance. Two days before a big race, consider drinking an additional 1-2 litres of electrolytes so that when you start your race, you will already be adequately hydrated. Monitoring the colour of your urine can also be a useful indicator of your hydration status—aim for a light, pale yellow colour.

Choosing the Right Foods for Optimal Performance

Selecting the right foods is essential for optimising performance and recovery in marathon training. Focus on nutrient-dense options that provide a balance of macronutrients and micronutrients. Prioritise whole grains, lean proteins, healthy fats, and plenty of fruits and vegetables to meet your dietary needs.

Before a run, consume easily digestible carbohydrates to provide quick energy. Any run over 90 minutes will need fuelling before and during to maintain optimal energy levels. Fuel can also be consumed via liquid carbohydrates, especially in the latter stages of the race when it is harder to digest solids.

Post-run, focus on a combination of carbohydrates and proteins to replenish glycogen stores and promote muscle repair. Foods like bananas, oatmeal, lean chicken, and quinoa are excellent choices. Additionally, don’t forget to include foods rich in antioxidants, such as berries and leafy greens, to combat oxidative stress from intense training.

Lastly, beyond macronutrients, a well-rounded diet should incorporate essential micronutrients and plant compounds to enhance your health and performance. Iron supports oxygen delivery to working muscles, calcium and vitamin D help maintain your bone health under repetitive impact, while magnesium assists with muscle relaxation and recovery. Shortfalls in these nutrients may not be immediately obvious but can gradually impact your training consistency and increase injury risks.

At its core, sports nutrition is about providing the right balance of macronutrients to meet training demands and support your performance.

The Missing Link in Marathon Preparation

Many runners spend months building endurance and speed while overlooking training their gut. This can be costly.

Your digestive system plays a pivotal role in energy absorption and nutrient delivery, both of which are essential during long-distance running. Gut training involves gradually teaching your body to tolerate and absorb the foods and fluids you’ll rely on during races.

By repeatedly practising your nutrition strategy during long runs, your body becomes more efficient at processing carbohydrates under physical stress. This reduces the risk of nausea, cramping, bloating, or energy crashes on race day and ultimately helps you perform better!

This process also helps you identify whether gels, chews, sports drinks, or solid foods work best for you. A trained gut delivers energy more effectively to working muscles and your brain, exactly when you need it most.

The Timing of Meals: When and What to Eat

The timing of your meals can significantly influence your training performance and recovery. Pre-run meals should focus on easily digestible carbohydrates to fuel your workout. Aim to eat a balanced meal 3-4 hours before running, including a mix of carbs, proteins, and fats. For early morning runs, a small snack like a banana or energy bar 30 minutes prior can suffice.

Post-run nutrition is equally important for recovery. Consuming a combination of carbohydrates and protein within 30-60 minutes post-exercise helps replenish glycogen stores and kickstarts muscle repair. A smoothie with fruits and protein powder or a turkey sandwich with wholegrain bread are excellent choices.

Experiment with different foods and timing to discover what works best for your body. Keeping a food and training journal can help you track how different meal timings affect your energy levels and recovery.

Eat your Way to the Finish Line

Common Nutritional Pitfalls to Avoid During Training

Creating a Personalised Nutrition Plan

Creating a personalised nutrition plan involves understanding your unique physiological needs and training goals. Start by calculating your daily caloric needs based on your basal metabolic rate (BMR) and activity level. Online calculators can provide a rough estimate, but consider consulting a sports nutritionist for a tailored plan.

Incorporate a variety of foods to ensure a broad spectrum of nutrients and prevent dietary monotony. Prioritise whole, unprocessed foods over processed options to maximise nutrient intake. Pay attention to portion sizes and adjust based on hunger cues, weight fluctuations, and training demands.

Regularly assess your nutrition plan and be flexible in making adjustments. Factors like training intensity, seasonal changes, and personal preferences can all influence your dietary needs.

Speak to our expert team to discover how personalised nutrition planning can improve your marathon training and racing outcomes today.

Fuelling Each Training Phase

What you eat, and when, has a direct impact on your energy levels, comfort, performance, and recovery. Marathon training moves through distinct phases, each with different nutritional priorities.

• Building phase: focus on establishing a strong nutritional foundation with a balanced intake of carbohydrates, protein, healthy fats, and micronutrients. Prioritise whole grains, fruit, vegetables, and quality protein sources.

• Peak training phase: caloric needs increase as mileage and intensity of workouts rise. Prioritise carbohydrates to maintain energy levels and adequate protein to support muscle repair.

• Taper phase: slightly reduce calories as training volume falls (which naturally happens as your appetite will decrease), but maintain carbohydrate intake to keep glycogen stores full. This ensures you arrive at race day rested and fuelled.

• Recovery phase: the day after the race, prioritise easy-to-digest carbohydrates, hydration, and sufficient protein to accelerate repair.

In the three days leading up to the marathon, carbohydrate loading becomes important. Choose familiar, easy-to-digest foods, limit fibre and fat, and focus on consistent hydration. Keep alcohol to zero or as low as possible.

Ultimately, a well-planned nutrition strategy supports training by replenishing fuel stores, promoting recovery, and reducing gastrointestinal distress.

“Depending on the phase of your training, what you ask of your body changes – building resilience, adaptability, performance and recovery. Getting the right nutrition at each phase gives your body the support it needs to deliver,” states Clemence Cleave, Nutritionist.

Linia Patel, Dietitian and Performance Nutritionist at Pure Sports Medicine, adds, “Vegetables and fruit, which contain antioxidants, polyphenols, enhance recovery but also nourish your gut microbiome, a hidden ally to sports performance. A healthy gut supports nutrient absorption, immune defence, controls inflammation, and even has a role in mood and mental wellbeing. Active individuals with diverse gut microbiomes often recover faster and adapt better to training.”

Best Pre-Run Meals

Aim to eat a carbohydrate-rich meal with some protein around 3–4 hours before long runs to ensure that your body has the energy reserves needed for sustained activity.

Suitable options include:

• Porridge made with milk and topped with fruit and nuts

• A chicken or tuna sandwich on wholegrain bread

• Rice with eggs and vegetables

For Early-Morning Runs

When a full meal isn’t practical, maximise your meal the night before the race, or opt for a lighter snack 30–60 minutes before running to provide a quick and effective source of fuel:

• Banana

• Toast with jam

• Fruit yoghurt

• Small energy bar

These provide quick fuel while being easy to digest.

Fuelling During Long Runs: Avoiding the Wall

During long runs, maintaining steady energy levels is crucial to avoid hitting the infamous “wall.” Your body can typically store enough glycogen for around 90 minutes of running. Beyond that, additional carbohydrate intake becomes essential.

For runs longer than 90 minutes, aim to consume carbohydrates every 30–45 minutes using options such as:

• Energy gels or chews

• Sports drinks

• Easily digestible real foods (e.g. jelly babies, fig rolls, banana, flapjack)

Always take gels and chews with water to aid digestion and absorption. As with pre-run nutrition, in-run fuelling must be practised repeatedly in training to refine timing, quantities, and product choice to prevent any surprises on race day.

“On race day, the last thing you want is to experiment. Pack your own snacks and stick to what you’ve practised in training, adjusting for the weather if needed,” notes Clem.

Marathon Recovery Nutrition

Recovery is just as important as preparation. The right post-run nutrition restores glycogen, accelerates muscle repair, and reduces soreness.

“Post-run, your body is ready for both carbs and protein, so aim to include both in your recovery drink or meal. And don’t forget steady rehydration alongside it”, states Clem. Effective options include a glass of chocolate milk, smoothies with fruit and yoghurt, a banana and some protein powder, a chicken and quinoa salad, or a peanut butter and banana sandwich.

In general, incorporate anti-inflammatory and nutrient-dense foods like berries, leafy greens and tart cherry juice, which may help reduce muscle soreness and support your recovery.

How to Recover After Running a Marathon

A strong understanding of sports nutrition, tailored to your individual needs and training demands, can have a profound impact on your marathon performance and overall training quality. Nutrition is not an optional addition to marathon preparation; it is a vital component that underpins consistency and successful marathon preparation.

By understanding the importance of balancing calorie intake with calories burned, and by making informed nutritional choices, you can enhance your marathon training experience, leading to improved performance and faster recovery times. Embrace these strategies and watch as your marathon journey becomes not just a challenge, but a rewarding and successful endeavour.

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