10 Rules of Marathon Training Nutrition

In this post, we dive into marathon training nutrition and give our 10 rules for how to eat and fuel when in marathon training mode!

Whether you are close to race day or you are just beginning your training plan, it’s important that you are aware of the science behind sports nutrition so that you can fuel yourself with an ideal marathon training diet.

In fact, nutrition, in general, is now widely recognized to be just as important as training for any athlete. Therefore, for endurance athletes such as marathon runners, it is important to make sure you are not just relying on sports drinks for energy, but rather you are eating the right food and enough of it.

This is why we have laid out 10 rules for marathon training nutrition that you can use to help create your own marathon training diet. These rules are just as relevant for those training for a half marathon or ultramarathon.

Using these rules, you will be able to effectively fuel your runs, boost your recovery, and be in the best shape possible come race day.

Let’s jump in!

a healthy salad bowl

1. Understand your metabolic needs

Every marathon training plan involves running a high volume of miles to increase your aerobic capacity, but how many calories does this require?

During these training sessions – and on race day – runners can burn up to 100 calories per mile.

That’s 1,500 calories for a 15-mile training session.

These calories must be replaced as part of your marathon training nutrition plan.

A runner eating in a calorie deficit will begin to break down muscle to compensate.

This is bad news; our muscles are a storage container for vitamins, minerals, and carbohydrates, which we don’t want to lose too much of. Pairing this with the protein structure of muscle makes them the primary target for fuel when you don’t consume enough food.

Therefore, step one in marathon training nutrition is to make sure you are eating enough calories.

Also understand your calorie consumption varies slightly from day to day depending on the intensity and length of the training sessions, but overall training for a marathon means eating more food to ensure that your calorie intake is sufficient.

2. Keep Macros in Balance


A spread of different carbohydrates viewed from above

The primary fuel for marathon runners without a doubt is the carbohydrate.

This macronutrient should be make up the majority of what you are consuming, due to the fact that it is required to replenish the glycogen stores in your body that fuel your muscles.

During intense training phases (where mileage and tempo increase) the body will need more carbohydrates to fuel workouts and replenish stores.

Aim to eat between 3.5 – 4.5g per pound of body weight each day on these intense days. For a 120lb runner, this equates to 420-540g of carbs per day.

On lighter training days and rest days the goal for carb consumption should be between 3.0 – 3.2g per pound of body weight.

Try fueling with complex carbs such as whole grains, beans, and vegetables for a healthier carbohydrate option.


Protein is the next most important macronutrient to help replenish muscle breakdown. Adequate protein intake is necessary to help your muscles recover.

On training days, aim for 0.7 – 1.0g of protein per pound of body weight while non-training days should be between 0.5 – 0.7g per pound of body weight.

A spread of high protein foods including meat, fish, nuts, cheese, eggs, milk, avocado, and pulses.


Fat is the final macronutrient and is needed to help with vitamin storage and hormone production, but should be kept around 0.5g per pound of bodyweight on training and non-training days.

Whilst many people associate fat as something to avoid as part of any diet, it is undeniably important when training for a marathon. You can cook with foods high in unsaturated, healthy fats such as olive oil, nuts, seeds, and fish in order to get the fats you need when training for a marathon and keep your diet healthy.

Related: Running Rules: The 13 Unspoken Rules + Proper Running Etiquette

fat sources including avocado, nuts, oil, and fish

3. Obey the Eating Window

Long endurance runs will deplete carbohydrate storage in the body.

To help mitigate this, eat an easily digested carb-based snack 30-45 minutes prior to a run. A sports gel or piece of fruit is perfect. This also ensures that you’re not running on an empty stomach.

Within an hour of finishing your training session, replenish your carb stores by eating a full meal using the macronutrient quantities discussed above; roughly aim for 1 gram of protein for every 3-4 grams of carbs.

This rule is the key to keeping you fueled between training sessions and should be at the top of your list when considering marathon training nutrition.

4. Eat clean foods

Whole foods are the easiest for a body to digest and pull nutrients from.

Eating the cleanest sources of foods that are available to you will ease digestion and increase nutrient absorption, aiding in the recovery process of your marathon training.

When shopping for foods to eat during your marathon training go with organic, natural, and as close to whole foods as you can, and try to avoid processed foods.

a spread of whole foods viewed from above

5. Minimize added sugars

Almost all marathon runners-in-training turn to high-energy sports fuel such as energy gels and sports drinks. Whilst these can be a good source of race-day nutrition to help give you an energy boost, you shouldn’t rely on them during training, as your body needs more than this.

When picking these products keep an eye out for unnecessary added sugars. You want a quick source of carbohydrates but not all of the calories should come directly from sugar.

Find a lower sugar supplement that tastes good to you.

6Keep snacks on hand

As we’ve mentioned before, marathon runners burn calories like crazy.

To keep calorie count high, especially on training days, keep pre-packed healthy snacks with you wherever you go.

These snacks should fall under all the rules we’ve laid out thus far. They need to be primarily carbslow in added sugars, a clean source of energy, and perhaps most importantly, something you enjoy.

Packing snacks before the day starts gives you a plan to fuel your training and a reason to stay away from the candy bars.

a plate of pancakes with strawberries and strawberry jam and cutlery on the plate

7. Find the Right Foods

We all digest foods differently and if your stomach gets upset from a certain gel or has trouble digesting a particular food, then don’t eat it.

There’s no hard and fast rule saying marathon runners have to eat potatoes, or use brand X gummies, or nut butters.

Find what your body likes, can digest without issue, and stick to that.

8. Hydrate, Hydrate, Hydrate

Hydration is critical for muscle health (preventing cramps), body temperature regulation, as well as vitamin and mineral absorption.

When you’re out on the road putting your miles in, the body is losing a considerable amount of water through sweat; the average person will sweat between 0.8 and 1.4 liters for every hour of intense exercise.

Taking small sips of water every 15-20 mins during a run will go a long way to replace what is lost.

Electrolyte drinks can also be useful for replenishing salts and other minerals that are lost during dehydration.

a woman sipping a glass of water

9. Supplement Where Needed

Natural food supplements, such as ginger and fish oil, are great for joint health and inflammation.

These two supplements will aid in the recovery process and keep you on the road for longer.

Make them part of your marathon training nutrition plan.

In addition to those, BCAAs can be used to prevent muscle break down, while a multivitamin will provide B-12 to combat fatigue, D3 and calcium for bone health, and iron for better oxygen transport to the muscles.

10. Don’t Try Anything New on Race Day!

All these rules for a marathon training diet should be practiced during training!

Race day is not the day to try something new!

Practice fueling, hydrating, and experimenting with energy gels and energy sources prior to the day of your marathon in order to get the most out of your race-day nutrition.

a young lady and a man slightly behind her and to the right, both looking happy during a marathon race with a crowd of fellow racers stretching out behind them


Marathon training nutrition and half marathon training nutrition don’t have to be difficult, but they should be taken seriously.

Following these 10 rules for eating during your marathon training plan will increase your energy on the road, keep your muscles primed for training days, ensure you are getting the calories and nutrients your body needs, and prepare you for race day.

bonus tip! :

11. Have a Meal Plan!

Alright, I know we only said 10 rules, but the 11th – and possibly most important rule – is to have a Marathon Training Meal Plan in place.

Where to start?

Check out our completely free, downloadable marathon training meal plans!

We include:

  • Sample 1-week marathon meal plan
  • Sample ‘week before your marathon meal plan
  • Sample vegetarian 1-week marathon meal plan
  • Sample vegetarian ‘week before your marathon’ meal plan

Check out our marathon training meal plans!

Photo of author
Thomas Watson is an ultra-runner, UESCA-certified running coach, and the founder of MarathonHandbook.com. His work has been featured in Runner's World, Livestrong.com, MapMyRun, and many other running publications. He likes running interesting races and playing with his two tiny kids. More at his bio.

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