An expert guide to marathon training nutrition

Author: Laura Hilton

Read Time:   |  August 1, 2022

Getting your nutrition right when you're training for a marathon is important. Nutritionist Laura Hilton shares her expert guide to marathon training nutrition

Following a marathon training plan places huge demands on your body. But many of us don’t really think about the food we’re eating around our training, which can lead to poor performance, exhaustion and maybe even injury. It is therefore hugely important to tailor your diet from Week 1 of training, to ensure that your body has all of the nourishment it needs to keep you feeling healthy, energised and strong.

We asked nutritionist Laura Hilton for her expert advice on how much to eat, what foods to have on-hand and what to avoid during marathon training…

Do I need to eat more if I’m training for a marathon?

Many runners wonder if they need to eat more when they start training for a marathon, but the truth is that it depends. It depends on your activity level, how much you eat before you start training and your energy balance.

The term ‘energy balance’ relates to the amount of calories you consume versus the amount that you burn. If you burn the same amount as you consume your bodyweight will stay the same. If you burn more than you consume you will lose bodyweight. If you burn less than you consume then you will gain bodyweight.

In order to know if you need to increase your nutritional intake when you embark on marathon training, you need to know if you are currently in an energy deficit, balance or surplus. To find out, you will need to monitor your bodyweight. If it is stable, you are in energy balance. If it is decreasing, you are in an energy deficit. If it is increasing, you are in an energy surplus.

For marathon training, I’d recommend aiming for an energy balance. If you’re currently in that place, then yes, you will need to increase your food intake to match any increase in activity levels. If you’re currently in energy surplus, you may not need to eat more. The increased activity will soon match your food intake. If you’re currently in energy deficit, then you definitely need to increase your food intake. This will ensure that you have enough energy to deal with the extra demands of marathon training.

What should I eat while training for a marathon?

As always, you want to have a balanced, healthy(ish) diet while you’re training for a big race like a marathon. But there are some extra things to note when planning your meals:


The amount of carbohydrate you should be eating during marathon training is likely to increase. This is due to the extended duration and intensity of marathon training runs. Some of these extra carbohydrates will come from mid-run fuelling, but it’s also essential that you get enough carbs post-run.

Healthy fats

Monounsaturated or polyunsaturated fats are a great fuel source for long runs. Try and have two or three portions a day. We’re talking avocados, olive oil and nuts.


Protein is important when you are training for a marathon. It helps your muscles to make training adaptations, which is a fancy way of saying recovering after runs and ultimately becoming stronger. Here’s how much protein you should be eating as a female runner.

When should I eat around my long runs?

Knowing how long to wait after eating before you run can be tricky. You need to make sure your body has enough energy to run, but eating too close to your run can lead to discomfort and even runner’s trots. It’s important to experiment to see what suits your body best. As a starting point, try this:

Before a long run

3-4 hours before: a main meal (usually breakfast or lunch) with a focus on carbohydrates and a moderate amount of protein.

30-60 minutes before: a light, high-carb snack. Some people like to have a pre-workout drink, but a banana will also do just fine.

During a long run

If your run is longer than 90 minutes, it’s recommended to take on some more carbohydrates to keep your muscles well-fuelled. You can try sports gels or bars, and some runners swear by gummy sweets.

After a long run

Refuelling is important after a long run. Ideally you’ll be eating a combination of carbs and protein within an hour of your run. If you’re always starving afterwards, then this could be a full meal. If you feel less hungry than usual after you run, a snack would be fine – a protein smoothie or porridge are good options.

How much should I be drinking?

Unless you’re already regularly running marathon training distances, you’ll need to increase your hydration levels to replace lost fluids during your runs. A way of checking your hydration status at the end of a run is to look at your urine. It should be a light straw colour. If it’s darker than that, you’re dehydrated and need to take on more fluids.

Most of this extra hydration will need to come from water. When to drink it will depend on you and your bladder. If you tend to forget to drink water and don’t usually need to take a mid-run toilet stop, your run could act as a reminder to down some water. If you find that you are always needing to pee when you’re pounding the pavements, then it’ll be best to spread your extra water intake through the day to avoid a knock-on effect on your run.

Will marathon training help me lose weight?

I get asked a lot if running will help with weight loss. The answer is technically yes, but it does depend on a few factors. In order to lose weight, you need to be in an energy deficit, as explained above. Training for a marathon usually increases our energy expenditure. We often run a lot more often and further that we would have done previously. This makes it more likely that you’ll be in that energy deficit, which is why many of us assume we’ll lose weight while marathon training.

However, marathon preparation may not the best time for trying to achieve a weight-loss goal. Training is tiring, and being in an energy deficit will only make that worse. It could affect your performance, your sleep or even contribute towards injury. It can also lead to Relative Energy Deficiency in Sport (RED-S), which cause a whole host of unpleasant side effects.

What is RED-S?

If athletes are in an energy deficiency a lot of the time, then they are in danger of developing a condition known as Relative Energy Deficiency in Sport (RED-S). This can lead to numerous problems including fatigue, weakened bones, hair loss and fertility issues, amongst other things. It is therefore really important that you do not spend long periods of time in an energy deficit, which you can monitor by keeping an eye on your bodyweight throughout your training. If it is continually decreasing this is a sign that you are not eating enough and therefore in danger of developing RED-S.

Written by

Laura Hilton

Laura Hilton

Nutritionist, personal trainer and mum of three Laura loves running in the countryside with her dog and has taken on numerous marathons

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