What Should Be My Diet During Marathon Training?

What Should Be My Diet During Marathon Training?

There are so many aspects that go into marathon training. First off, there is the decision in making and choosing the right marathon course and season to participate in. Once you have decided where and when you will run, the ultimate commitment for the athlete comes from registering and paying for the race. Once the race has been committed to, next up is choosing the right marathon program and training gear. While your plate seems to be already full, ironically enough, an often neglected aspect of marathon training is providing yourself with proper foods and nutrition. 

What should your diet be like during marathon training? 

We have asked Registered Dietitian Nutritionist (RDN) Diana Reid, who has her Master's in Public Health and is the owner of The Global Dietitian, her advice on good sports nutrition.

We all know the physical training that must be incorporated over time when planning for a marathon but sometimes there is confusion on what is involved with proper fueling.  Good nutrition plays a vital role in athletic performance, helping to prevent injury and provides faster reparation of tissues. If we neglect our nutrition, we may feel more fatigued putting ourselves at a higher risk for an injury which in turn can affect overall performance.

There are several different factors to consider when creating a nutrition plan including the size of the athlete, distances of training runs and races, level of intensity required within a workout, and external factors such as weather and course difficulty. However for the most part, Diana suggests a balanced nutrition regimen for endurance runners consisting of complex carbohydrates, protein, and some healthy fats along with adequate hydration. 

How does that all break down when it comes to training for a marathon?

When it comes to running, carbohydrates are the ultimate energy source while protein is good for building muscle and recovery of tissues. Below you will find Diana's detailed information for runners, guiding us what to eat and when while emphasizing the focus on carbohydrates (carbs) and protein.


Avoid foods that have gluten, that are high in fiber or caffeine content, a lot of fat or are very spicy, and alcohol to avoid gastrointestinal (GI) issues. 

2-4 hours before activity: eat a balanced meal of 120-200g of carbs, 15-25g of protein, and healthy fat plus 300-500ml (10-17oz) of water.

Depending on your size and weight, the range of carbs to protein varies. If smaller in size, opt for the lower recommended range and if bigger, shoot for the higher range.

Some food examples include: 



bagel (50g)

beans (35-40g)

oatmeal (30g)

banana (27g)

apple (25g)

grapes (25g)

dried fruit (15g)

turkey (34g)

chicken (32g)

salmon (23g)

greek yogurt (17g)

milk (8g)

egg (6g)

nut butter (3.5-4g)

30 minutes to 1 hour before activity: smaller snacks with about 30-60g of carbs plus 500 ml (17oz) water.

Some food examples include: 

  • granola bar (25g)

  • multigrain bread (15g)

  • clementine (15g)

As runners, many of us have heard of the term “carbo-loading” and use it as an excuse to eat as much pasta and bread as we want the night before a race but realistically Diana states this could ultimately make you feel worse. Instead, she suggests adding just an extra serving of carbs each day, a few days before the race as being sufficient enough. 

Diana reminds us to experiment and practice what we will eat and drink during our weekly long runs leading up to the race. Good preparation and recovery also includes not only what you eat pre- and post-run but also during. Practicing your race nutrition during your long runs will be essential to help you determine your energy levels and also what your stomach will tolerate. No one enjoys a race day if they end up having GI issues. Therefore, finding the right balance of fluids and carbohydrates during your training runs are something that needs adequate practice leading up to race day. 

During the Run:

Focus on 30-80g of carbs, depending on the duration of the run, and hydration about 250ml (3-6oz) of water every 15-20 minutes (or every 2 miles) and a couple large sips of carbohydrate sports drink every 15-20 minutes during long runs and hot races. Do not drink TOO much water as this can cause hyponatremia (low sodium levels in the blood), one guideline is to not exceed 600ml (20oz) of water per hour.

Run times:

< 1 hour to 1:15 hours: no fuel is needed if properly pre-fueled, 250ml (8oz) water every 15-20 minutes.

Between 1:30 hours to 2:30 hours: 30-60g carbs per hour, 250ml (8oz) water and a large sip of sports drink every 15-20 minutes.

> 2:30 hours: 80g carbs per hour, 250ml (8oz) of water and a large sip of sports drink every 15-20 minutes.

Some food examples include:

  • energy gel (20-40g)

  • sports drink (14g)

  • orange (15g)

  • jelly beans (11g)


If an easy run is less than 45 – 60 minutes, carb refueling is not required. However, if the exertion level was high intensity or the run was longer than 1 hour, a drink or snack with a combination of both carbs and protein is best for recovery plus 175-300ml (6-10oz) of water every hour for a couple of hours following training/race.

within 30 minutes after activity: About 3:1 carbs to protein ratio per kilogram of body weight. Avoid alcohol up to 2 hours following activity.


60kg (132lb) - 60g carbs, 20g protein 

80kg (176lb)  - 80g carbs, 25g protein 

100kg (220lb) - 100g carbs, 30g proteins

Some food examples include:

  • chocolate milk (50g C, 20g P)

2-4 hours after activity: a full meal with balanced carbs, protein, and some healthy fats plus water as normal with meals. 

In conclusion, Diane offers runners some final thoughts:

  • Train the way you plan to race. Eat what you know works for you during training. Your gut doesn't like surprises on race day.

  • Don't be scared of carbohydrates. Low carb and Keto diets are all the rage these days, but they are not sustainable. Your muscles need a good supply of glycogen to perform in endurance activities.

  • Hydrate well, but don't over-hydrate. Try to practice your hydration strategies the same way you would practice your food strategy. Assess your typical fluid loss during training by weighing yourself before and after training to determine how much you need to take in to replenish fluids. Also, be sure to factor in external circumstances like weather and course difficulty which may mean you need to adjust your fluids more diligently.