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Run it as you eat it! How to nail your marathon with some nutrition and hydration advice

You have probably run around 300 miles in the last months, asking your body a lot, and now that we are in the training peak weeks, you should also make sure you are fueling and hydrating properly to ensure your body's wellness and to nail your race!

Nutrition is a complex topic and we are not aiming at being exhaustive here. The goal of this blog post is to give some generally accepted advice on hydration and fueling for endurance events. If you have specific health-related questions on your diet, contact a Registered Dietician.


Marathon Hydration and Fueling strategies begin during your training as you need to adapt your body to new hydration and nutrition habits, you need to test different strategies for race-day in advance and also because a long run above two hours requires fueling and hydration care, just like a race.


Let's start with some Hydration advice and some commonly asked questions

How much and how often should I drink water before, during, and after the marathon or long run?

Drink 300-500ml (10-16 oz) of fluids 1-2 hours before exercise, add 100-200ml (4-7 oz) right before the start. During the race or long run, it is recommended to drink 100-200ml (4-7 oz) every 15-20min. Don't forget that you need to replenish what you lost after the race - you will need about 1.2-1.5 liter of fluid for each kg of body weight lost (18-22 oz of fluid for each pound lost). These are general recommendations, and you should use your body weight and your estimated sweating rate to build your personalized hydration plan. Make sure that you do not lose more than 2% of your body weight during exercise.



How can I estimate my sweat rate?

You can measure your sweat loss as follows:

SWEAT LOSS (liters/oz) = body weight before exercise (kg/lb) – body weight after exercise (kg/lb) + fluid consumed during exercise (liters/oz)

Example on 1 hour exercise: 60 kg before – 59.5kg after + 0.5kg(half liter) of fluid consumed during = 1 liter of sweat/hour. Or 120 lb before - 119lb after + 1 lb(16 oz) of fluid consumed during = 32 oz (2 lb) of sweat/hour


Should I count sports drinks in my fluid intake?

YES! Sports drinks and electrolytes tablets/powder dissolved in water count when we consider fluid intake.


Should I rely on thirst on race day or long runs?

NO! Follow a schedule, design your own hydration strategy in advance. Drink early and often, practice your strategy during your long runs. Use your body weight and your estimated sweat rate to build your own hydration plan to avoid dehydration and hyponatremia.

DEHYDRATION: unusual fatigue, weight loss >2% of body weight, headache, dizziness, nausea, dry mouth, and lips.

HYPONATREMIA (over hydration): unusual fatigue, weight gain, confusion.


How do I know if I am properly hydrated?

Check your urine! Dark yellow urine is a sign that you are dehydrated and that you must drink more fluid.


Next, let's talk about Electrolytes

What are electrolytes and why do I need them?

Sodium, potassium, magnesium, calcium, chloride, and phosphate are electrolytes, minerals that carry an electric charge when dissolved in a liquid. They help regulate nerve and muscle functions and play an important role in regulating water balance.



Can I just drink water?

When we sweat, we lose electrolytes together with water. Electrolytes help our body retain water. If we don’t replenish the electrolytes lost with the sweat, we can’t hydrate ourselves properly.


What is the recommended intake?

  • Sodium is the electrolyte that athletes need the most during activity: 200mg-400mg per 1 hour of activity

  • Potassium: 150mg-400mg per 1 hour of activity (a lack of it can cause cramps during activity)

  • Calcium: 1100mg daily for 18-50yo – 1200mg-1300mg > 50yo

  • Magnesium: 300mg-350mg daily for women, 400mg-450mg men, 500mg-800mg for athletes

How can I take my electrolytes during the marathon (or long run)?

  • Sports Drinks (but be mindful of the carbs)

  • Energy Gels with electrolytes included (HUMA Plus, GU Roctane)

  • Electrolytes Tablets/Powder (Nuun, Skratch)

  • Salt Tablets/Caps (SaltStick)

What are the signs of electrolytes deficiency?

Dizziness, cramps, fatigue, headaches, mental confusion, confusion, irregular heartbeat.. All things that it’s better to avoid during a marathon!


Last but not least, let's cover fueling

Before the marathon/long run: carb-loading.

During the marathon/long run: consistent replenishment of glycogen.

After the activity: refuel with carbs, repair with proteins.


Fueling Before the activity: What is Carb-Loading and why is it important?

During many types of exercise, your body uses stored carbs to provide you with energy.

In the body, carbohydrate stores are called glycogen. This glycogen is mostly found in two places: your liver and muscles. Carb-Loading is simply a nutritional strategy to increase the glycogen stored in your body above its normal amount.


Fueling Before the activity: Does Carb-Loading mean that I can eat all the pasta I want the day before the race?

Not really! You should slightly increase your carbs intake for the whole week preceding the marathon. The day before the race, make lunch your “big meal” and avoid eating too much for dinner. Avoid too many fibers and fats (they slow digestion down and may cause gut issues) and anything that can cause distress on your gut. Good options for a pre-marathon meal are pasta, pizza, noodles, rice, baked potatoes. Carb-loading is particularly effective when you are reducing your training load (during your tapering weeks).

Photo by Aleksandra Tanasiienko


Fueling Before the activity: Apart from Carb-loading, should I avoid carbs during my normal diet and during training? Should I only eat proteins

NO! A balanced diet is important, and it should include carbs. Also, during your long runs, your body will need and use your stored carbs (glycogen) from your liver and muscles as well! Do not forget proteins. Endurance athletes (e.g. those training for a marathon) should consider raising their protein intake to between 1.0-1.6g per kg per day to aid muscle recovery. This is important during training and after the race. As an example, a runner of 60 kg (132 lb) should eat about 60-96 gr protein per day. Animal food contain proteins are more complete as they have more complex amino acids contents and often more iron, but also more fat. Legumes are great but you should add some animal protein unless you are vegetarian or vegan. Some examples of high protein foods that are not meat are Parmigiano Reggiano and other hard cheeses (about 10 gr per portion), tuna, cod, and fish in general (about 20-30 gr per portion, the same as beef), beans, and lentils (around 20 gr per portion), oat (10 gr per portion), pine seeds, and pistachios (10 gr per portion). You have to consider the daily intake and try to be balanced with proteins, iron other minerals intake on one hand and avoiding fat and cholesterol on the other.


Photo by @master1305


Fueling During the activity: How much and how often should I eat during the marathon?

Glycogen is a carbohydrate that is stored in our muscles and liver for energy. It is the easiest and most readily available fuel source to burn when exercising. A general recommendation is 30-60g of carbs every hour. It could be up to 90g per hour for an effort of 4-5 hours.


The serving size of energy gels is usually around 23-25g of carbs. One gel per hour may not be sufficient to replenish your stored glycogen and give you the energy needed to sustain a continuous effort. Read the nutrition facts on the labels.



Fueling During the activity: How can I choose the right energy gel for me? What if I don’t like any of them, can I have another snack instead?

You can choose between gels, energy chews, energy bars, and sports drinks. But read the labels! You are better off with products that are:

  • Low in Protein

  • Low in Fibers

  • High in Carbs

  • With some electrolytes included (if possible)

Fueling During the activity: What is “the wall” and is it real?

YES, the wall is very real! When endurance athletes run out of glycogen, their performance almost immediately begins to suffer, and they feel they cannot continue, this is commonly described as "hitting the wall”.

How can we beat the wall?

  • Carb-loading: you want to make sure you have stored glycogen in your muscles and liver.

  • Good breakfast on race day (and long-run day): do not rely just on fueling during the race.

  • Right fueling strategy during your race (and long runs).


Fueling During the activity: Is caffeine good for runners?

Yes, most of the times! Caffeine increases alertness, energy, focus and it's effective in reducing perceived exertion. Athletes who don’t often use caffeine should start with a low dose (25mg) and see how they respond. Alternating gels or chews with and without caffeine is preferable.


It is a good idea to test how your body reacts to caffeine during the training


Fueling After the activity: What should I eat and drink after a long run or after the Marathon?

  • Refuel – Have a carbohydrate-rich snack followed by a meal soon after the race.

  • Rehydrate – Replace fluid losses by drinking at regular intervals post-race.

  • Repair – Include a serving of protein with your recovery meal.

  • Rest – Get a good night’s sleep – this is when most of your muscle repair will occur.

Bonus questions: Race Day strategy - NYC Marathon 2021

What should I eat the morning of the marathon? And when?

Nothing new on race day! Have the same breakfast you tested before during your long runs and had worked well. Avoid food rich in fiber and protein, prefer food rich in carbohydrates.

Examples of pre-marathon (or pre long runs) breakfast:

  • Plain bagel, toast, bread with peanut or almond butter

  • Oatmeal or low fiber cereal with honey

  • Banana or Juice

Have your breakfast from 3 to 1.5 hours before the start. You want to avoid having your food sitting in your stomach at the start!

How often should I take my gels/chews?

The recommended dose of carbohydrates per hour is from 30g to 90g.

Considering the standard serving of a gel is 21-25g of carbohydrates, take your gel/chews every 35-45 minutes. It's better to eat small amounts of carbs frequently than a large amount all at the same time! Avoid taking more than 60g in one serving, it will be hard on your digestive system and might cause GI issues. Be careful that the sport drinks provided Gatorade Endurance provided at the fluid stations contains carbs. Try it in advance if you plan to use it during the marathon, do not try anything new on race day.


How often should I stop at the fluid station?

Fluid stations are located at the mile markers. It’s not recommended to skip many fluid stations in a row: for endurance events, such a marathon relying on thirst could be tricky.

A valid strategy could be planning to stop at the even miles only and eventually stopping at the odds miles if needed. It’s always better to have your own water bottle that you can refill at the fluid stations. Remember that you should take gels/chews with water!






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