Fuel your running - what should you eat before you run?

Updated: Jun 23, 2020

What should you eat before you run?

It can be difficult to know what exactly what you should be eating before your run. How many carbs? Or should you go low carb? What about hydration, how much water should you have and do you need electrolytes? In this post, we’ll explain how and what you should be eating to fuel your running performance.

Although your collective diet will have the biggest impact on performance, understanding proper pre-workout nutrition will help ensure you are fully fuelled for your races and help you recover more readily.

When speed is the goal, carbohydrates are the preferred fuel for running (they produce a higher yield of energy per L of oxygen), however the amount that you need for each session will depend on you as an individual, the goal of the session, its duration and intensity.


The intensity of your run will dictate your carbohydrate needs. Harder sessions like threshold, interval runs and races will require fuelling with carbohydrates making it important to top off your glycogen (stored carbohydrates in your muscles) beforehand.

Easy and recovery runs won't require as many carbohydrates and what you eat day-to-day will cover your needs.

How to determine what requires more carbohydrates?

Your aerobic threshold (AeT).

Not to be confused with your anaerobic threshold, your Aerobic Threshold (AeT) acts as as a good indication of when you begin to use carbohydrates as the main fuel source. This is normally around the top of Zone 2 (using a 5 zone method) or around 65% of your VO2 max.

Unfortunately, as we're very individual, these arbitrary numbers don't always match what is actually happening. As you can see from the images below, two athletes switch to carbohydrates as the primary fuel source at different points. The purple shaded area indicates carbohydrate usage, whereas the yellow shaded area highlights fat being used.

This is reason why metabolic testing is the most accurate way to establish your personalised zones and fuelling strategy.

For workouts with an intensity lower than zone 2 (aerobic threshold) then it won't be necessary to adopt any acute fuelling strategy. As previously mentioned, what you eat on a day-to-day basis will be sufficient. However, for sessions that reach beyond the AeT, so threshold runs, intervals and speed work will require more carbohydrates and a carbohydrate rich pre workout snack or meal.


The length of your run will also dictate how many carbohydrates you require. As a guide, workouts that last beyond 60mins will require some sort of fuelling. As intensity will dictate the speed at which your glycogen stores deplete, low intensity runs won't need quite as many as a hard run.

Aim to have enough kcals from carbohydrates to fuel the whole of your training sessions, on top of your typical requirements (kcals/macros) for the day. Carbohydrates are needed for daily activities too! There will be exceptions to this rule if your goal is weight loss, or the purpose of the session is to instigate metabolic adaptation through training under low carbohydrate conditions (a topic for another day!).

Ok so what should you eat before your run?

For an in depth detail about how to fuel your different running sessions check out this video below:

Pre-run nutrition

Your pre run meal helps ‘top off’ depleted carbohydrate stores and ensures you have enough fuel for your session.

For shorter harder sessions (under 60mins) a good starting point is to aim for 1g per kg of your target bodyweight of carbs. For longer sessions < 60mins then look to consume 1-3g per kg of bodyweight of carbohydrates (Nutrition and athletic performance 2016, Hargreaves et al., 2004). This could come from a combination of meals and snacks.

Try and eat a balanced meal 2-3 hrs before your session. This gives you plenty of time to digest your food and avoid any stomach discomfort. Look to include foods that you would typically eat like porridge oats, bagels, toast and cereal for breakfast, or pasta, bread and rice for lunch. Try and avoid foods that are high in fat and fibre to reduce any gastrointestinal (tummy) problems. Spicy or acidic foods may also lead to discomfort during running. The key here is to practice your pre-race meal so you can find a setup that you know works well.

You may also consider a smaller snack such as a sports drink, carbohydrate chews/gel, fruit, or a cereal bar 15-45 minutes prior to your session. This can help top up blood glucose and help ensure you have plenty of energy.

For your easy and recovery runs, simply opt for meal or snack of your choice, your overall quantities for the day matter most and you don't need to think about any specific quantities beforehand.

Can’t eat before you train?

If you are training early and a big meal is impractical, fuel your session with a large carbohydrate meal the evening before. In the morning have a smaller liquid or semi liquid snack like a smoothie, shake or yoghurt that can be easily digested.


A 2% drop in body weight due to water loss can hinder both cognitive function and exercise performance. Although there are individual differences amongst athletes, we recommended that you drink around 5-10ml/kg of bodyweight 2-4 hours before exercise, or 500ml for easier runs and upto 750ml for harder runs and when it is warmer.

It is also good practice to include electrolytes in your pre workout drink. For harder, longer sessions then up to 1500mg/l of sodium is recommended although this will be less for easier, shorter events. Gaining an understanding of your sweat rate throughout the year helps identify your electrolyte needs.

Key points

  • Eat a combination of foods high in carbohydrates and moderate in protein

  • Eat foods that are low in fat and fibre.

  • Your plan will depend on the length and intensity of the session.

  • If you cannot eat beforehand, fuel the night before and eat something small and easily digestible in the morning

  • Experiment your fuelling plan in training to figure out what works best for you

For more help with your fuelling and performance, then check out Endure.

Box Endure is a testing and nutrition coaching programme for the recreational, amateur and age group endurance athletes, and CrossFit athlete’s looking to improving their capacity. Providing metabolic testing (VO2 max, thresholds and heart rate zones), nutrition coaching and strength and conditioning, Endure uses elite level testing that will help you get the most out of your endurance performance helping you become fitter, faster and stronger.

Find out more and sign up at https://www.boxendure.co.uk/plans-pricing

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