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Fueling for Training: The Foundations of Running the London Marathon
The Golden Rule for Running the London Marathon
The Basics: Build Your Plate
Fueling Before Your Run
The Digestion Spectrum
Injury Prevention & Physical Prep
Healthy Meal Delivery
The Basics: Build Your Plate
Fueling Before Your Run
The Digestion Spectrum
Injury Prevention & Physical Prep
Healthy Meal Delivery
With the London Marathon 2026 just around the corner, we’re launching a three-part series to help you run your best. We will cover:
- Fueling for Training & Foundations
- Do I Really Need Gels & Electrolytes
- Recovery & Post-Race Nutrition
It’s important to understand that nutrition during marathon training is very different to general nutrition advice.
It isn't just about fuel; it’s a performance tool that impacts your speed, endurance, and injury risk. When you are properly fueled, your perceived effort decreases, and the same pace feels easier because your body has what it needs to execute.
This article will explain core principles to follow during your marathon training block.
Running the London Marathon: Golden Rule for Energy Intake
The most important principle of marathon training nutrition is simple: Eat enough. The training places immense stress on the body. Your job is to make your body feel safe and supported. When you don't eat enough, you risk Low Energy Availability (LEA). This is where your body enters survival mode, prioritising basic life functions (heart, brain) over your performance and repair.
The Consequences of Underfueling:
The marathon training diet must include the needed nutrients to avoid health risks. Here’s what happens when you’re not eating well:
- Chronic fatigue and heavy legs
- Increased risk of stress fractures and soft tissue injuries
- Hormonal disruption (including loss of menstrual cycle or low testosterone)
- Impaired muscle recovery (Wasserfurth et al., 2020).
It is normal and necessary to eat more during marathon training. Surprisingly, if you eat less while training more, you could actually see weight gain compared to when you fuel correctly. This confusing concept is due to metabolic adaptation: when the body feels under-supported, it enters a survival mode, holding onto energy more efficiently because it knows it has to train hard again soon. By fueling adequately, you signal to your body that it is safe to perform, recover, and maintain a healthy metabolic rate (Espinar et al., 2026).
Build Your Plate: The Basics
You don’t need complicated recipes or perfect meals. Instead, focus on building your plate at every meal with:
- Carbohydrates: Your primary fuel source, especially in endurance exercise.
- Protein: For muscle repair and recovery.
- Fats: Essential for hormone health and long-duration energy.
- Fibre: Micronutrients from fruit and veg to reduce inflammation.
Carbohydrates (Your Primary Fuel Source)
Carbs are the most efficient way for your body to produce ATP (the energy molecule). As your weekly mileage goes up, your carb needs must go up too.
- Don't fear the beige: Pasta, rice, potatoes, and oats are your best friends.
- Include them at every meal: Consistency prevents "bonking" in your running sessions.
Protein (For Repair & Recovery)
Running causes micro-tears in muscle tissue. Protein is the building block that fixes them.
- The Target: Aim for 1.2g – 1.6g of protein per kg of body weight daily.
- Important: Protein supports recovery, but it doesn't fuel the run itself, and it should not displace other more important macronutrients in your diet, like carbs.
Fats (Essential for Hormones & Endurance)
Fats are vital for bone health, hormone production and absorbing vitamins (A, D, E, and K). Aim for 25–30% of your daily intake from healthy sources like olive oil, nuts, seeds, and oily fish.
- Avoid high-fat meals immediately before a run, as they take longer to digest and can cause digestive problems.
Fibre & Micronutrients
A simple rule is to aim for half your plate to be filled with fruits and vegetables.
These provide essential vitamins, minerals, and antioxidants to support recovery and reduce inflammation.
However, avoid high fibre close to runs to reduce the risk of bloating or discomfort.
London Marathon Nutrition: Fueling Before Your Run
For any session over 60 minutes, pre-run fueling is essential to maintain training quality.
30–60 Minutes Before: Focus exclusively on simple carbohydrates. These are rapidly absorbed and minimise the risk of gastrointestinal distress.
- Recommended: Toast/bagel/crumpets/hot cross buns with banana and jam
- Avoid: High-fat, high-fibre, and high-protein. These slow down digestion and are the primary cause of stomach cramping during high-intensity efforts.
- Avoid fasted runs for long-distance sessions. Marathon training is about teaching your body to process fuel under stress, not just running on empty.
The Digestion Spectrum: Structuring the Meal
Think of your pre-run meal in layers to ensure both immediate and sustained energy delivery.
Target Intake: Aim for 1–4g of carbohydrates per kg of body weight 1-4 hours before running. As your mileage increases, your pre-run breakfast should scale accordingly (Naderi et al., 2023).
If you struggle to eat early, Drink 300ml of fruit juice. This provides about 25–30g of carbohydrates, roughly the same as a standard energy gel.
Injury Prevention & Physical Prep
Nutrition fuels the run, but your physical preparation ensures you can prevent injury, the last thing we want in a training block.
1. Training Load
Avoid increasing mileage or intensity too aggressively. Consistency is more important than intensity. Your cardiovascular fitness often improves faster than your tendons and ligaments can adapt.
2. Muscle Activation
Prioritise active mobility before you run rather than static stretching. Focus on:
- Glutes
- Ankles
- Hamstrings
Many common injuries, such as knee pain, are often symptoms of weakness in the hips or glutes. Activation wakes up these muscles to provide better stability. It is not too late to make this part of your routine - especially on race day!
3. Strength Training
Strength work is a requirement for marathon runners, not an optional extra. It improves the economy and builds resilience. Focus on unilateral (single-leg) movements to fix imbalances:
- Single-Leg RDLs
- Single-Leg Glute Bridges
Healthy Meal Delivery: Ready to Fuel Like You Mean It?
Training for running the London Marathon 2026 takes more than discipline, it demands consistency, precision, and the right fuel at the right time. That’s where many runners fall short. If you’re juggling training, work, and life, Calo takes the pressure off your plate, literally. No more stressing over what to eat before or after your runs.
With the Calo App, you get meals designed to power your long runs and support your recovery. No guesswork, no time spent tracking every gram, and no compromises on flavour or variety. When your nutrition is handled, your focus sharpens, and your goals get closer.
Looking for Healthy Halal Food That Fits Your Training?
Staying consistent with your nutrition is easier when it aligns with your lifestyle. With Calo, you get healthy halal food without the extra effort. From balanced meals to convenient halal meal delivery, everything is taken care of, so you can focus on your training, not your meal prep.
Eat well. Stay consistent. Keep it halal, with zero compromise.
Final Thoughts on Running the London Marathon
Fueling for running the London marathon requires intentional planning. Your body is being asked to do something incredibly demanding, and how you support it will directly shape how you perform and recover.
Eat enough to meet the metabolic demands of your training. Prioritise carbohydrates as your primary fuel, and don’t overlook the role of consistent strength and activation work in supporting recovery and resilience.
Your body is capable of incredible things. When you fuel it well and support it properly, a PB could be in reach!
Read about stretching exercises and more about the benefits and downsides of running a treadmill here, or explore more health-related topics on the Calo blog.
References:
1- Wasserfurth, P., Palmowski, J., Hahn, A. and Krüger, K. (2020) ‘Reasons for and consequences of low energy availability in female and male athletes: social environment, adaptations, and prevention’, Sports Medicine - Open, 6, p. 44.
2- Naderi, A., Gobbi, N., Ali, A., Berjisian, E., Hamidvand, A., Forbes, S.C., Koozehchian, M.S., Karayigit, R. and Saunders, B. (2023) ‘Carbohydrates and endurance exercise: a narrative review of a food first approach’, Nutrients, 15(6), p. 1367.
3- Espinar, S., Sánchez-Fernández, M.A., Martin-Olmedo, J.J., Rueda-Córdoba, M. and Jurado-Fasoli, L. (2026) ‘Rethinking energy availability from conceptual models to applied practice: a narrative review’, Nutrients, 18(3), p. 379.
