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Marathon Race Nutrition

Gazelle Nutrition Lab / Blog  / Marathon Race Nutrition

Marathon Race Nutrition


Marathon season is in full swing and it’s time to start planning your race day nutrition. I’m excited to help get you set for a seamless performance. Read ahead for the first 2 steps of 5 to lock down your race day nutrition plan for your marathon.

Step 1: Calculate What You Need

If you’ve read my previous posts you know nutrition is not an exact science. Even so, it’s important to do the math to find out your ballpark fluid and carbohydrate needs and to decide how you’re going to meet these needs.


Striking the Balance

Drinking the right amount of fluid can get tricky. If you drink too little and lose more than 2% of your body weight this can impair your performance, if you drink too much, especially if you run slower than a 4-hour marathon you run the risk of developing exercise associated hyponatremia (EAH).  The answer is three-fold:

  1. You should drink to thirst. Avoid drinking so much that the liquid is sloshing around and you start to feel nauseous.
  2. Do your homework before your marathon. Figure out your personal sweat rate by weighing yourself before and after you go for a run. You require approximately 2-3 cups of fluid for every pound you lose during exercise.                                   Consider This Example: Based on your weight, you learn that you typically lose 1 pound per hour, which means you need roughly 2 cups (or 500 ml) per hour of running. This would translate into about ½ cup of fluid every 15 minutes. Also, be mindful that you don’t need to rehydrate to 100% of your fluid losses. Your goal is to avoid dehydration of greater than 2%.
  3. Use sports drinks or fluid that contain some salt. Sodium helps with fluid absorption and repletes losses in sweat.

Expert Fluid Guidelines

In general, consensus among nutrition experts has led to the following guidelines:

  • 4 hours before exercise – Drink 1 to 2 cups of fluid
  • 2 hours or less before exercise – Drink ½ to 1½ cups of fluid if you are dehydrated (i.e., you have not urinated, or you have only produced a small amount of dark urine)
  • During exercise – Sip fluid during your activity. Avoid gaining weight
  • Immediately after exercise – If you lose weight drink 2 to 3 cups for every pound of weight lost (or 500-750 ml for every 0.5 kg)


When you are running for more than 2 hours, taking in carbohydrates provides a myriad of benefits. Carbohydrate ingestion will keep the sugar in your blood stable, reduce liver and muscle glycogen breakdown, enhance performance, and delay feelings of fatigue. 

How much food should you aim for? The consensus is that for exercise between 1-2.5 hours you should ingest up to 60 grams of carbs an hour.  For exercise lasting longer, you may try and aim for up to 90 grams of carbs an hour. Regardless of body size, your body can use approximately 60 grams of carbohydrates an hour, higher if you use multiple carbohydrate sources. To find out more about multiple carbohydrate transporters click here

Consider This Example: Assuming you’re shooting for 60 g of carbs an hour you now need to decide how you’re going to consume this amount. Here’s one way you could do this every hour:

  • One gel – 25 g carbohydrate
  • 2 gummies- 10 g carbohydrate
  • 2 cups sports drink – 25 g carbohydrate

Despite what you may have heard, it’s best to start taking in carbohydrates shortly after you settle into a pace (say 15 minutes or so). Your body needs time to digest even gels and liquids so don’t wait. I like to sip on sports drink at the beginning but figure out what works best for you.

Can’t get to 60 grams of carbohydrates an hour?  Don’t fret. Many runners have trouble eating this much even when they’ve trained their gut. Rest assured that performance benefits have been observed at a range of intakes. Anywhere between 40-90 grams carbs an hour has been found to be helpful.

Step 2: Practice

Practice with Types of Carbohydrate


Your gastrointestinal (GI) tract can adapt and improve its absorption capacity. Nausea, cramps, and diarrhea are common during times of physical exertion. Food and fluid can exacerbate these symptoms.  Give your GI tract a fighting chance by regularly taking in food and liquid before, during, and after you run.

While gels are a popular source of carbohydrates, they are not the only source. Here are some other ideas:

  • gummies
  • sports drinks
  • bananas
  • colas
  • sports bars

Sports bars and gummies have the disadvantage of needing to be chewed while you’re short of breath. But if you like to take walk breaks they may work well. Liquids have the advantage of clearing quickly from your stomach. The disadvantage of liquids is that they can slosh around if you drink more than you can absorb so pace your consumption accordingly.

If you are using commercial products, they come in a variety of flavours and brands. Some people find they tolerate specific brands and flavours better than others. Try out a few types and combos to figure out what works best for you.

Practice with Timing

Is it your first time eating food while running? Start with small steps then.  Use a short run to test the water.  First practicing eating during a short run allows you to figure out if you’re prone to GI upset while you’re close to home. It also allows you to figure out how best to carry your food.

You could, for example, start small by bringing a gel along on a quick recovery run. Use one gel and take part of it at the beginning (within 15 minutes of starting out), middle and near the end of your run. This strategy can get messy. You can hold the gel, take it along a small sealable plastic bag, or mix the gel with water in one of your water bottles. Be sure to drink at least 1 cup of water for one gel.

Once you have an idea about your tolerance for different foods, practice using them during your long runs. You may even find it helpful to trial your food choices during your faster, shorter interval workouts. You will get a great idea of what foods are best when you are pushing yourself physically.

What’s next for Marathon success? You can find Steps 3, 4 and 5 in the Gearing Up For Marathon Post coming soon (add link when we have it!). Nutritional planning is integral to achieve your optimal athletic performance. Gazelle Nutrition Lab delivers one on one or group nutritional counselling and consulting to both recreational and high performance athletes.  Have questions? We’d love to hear from you! Get in touch!


Ashley Leone

Ashley is a Sports Dietitian and Owner of Gazelle Nutrition Lab. Ashley provides nutrition advice and plans to athletes and everyday active people alike. Her goal is to help fuel your inner athlete and put good sense back into eating. Ashley is an enthusiastic and knowledgeable nutrition specialist with over 20 years of experience.

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