How to Fuel for Marathon Training Runs

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Learn how to fuel double digit marathon training runs so you’re properly nourished on race day.

By Tamar Kane (Reviewed by Natalie Rizzo, MS, RD)

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If you’re a runner, you’ve probably heard people discuss their marathon fueling plan. Some people swear by oatmeal, others love gels, and some scarf down milk and cereal before the starting gun goes off. 

The good news is there are miles and miles of training runs leading up to that race to practice your fueling plan. Those 18 and 20 mile long runs before the marathon are really the dress rehearsal for the big day.

Just as you might try out a pair of socks on a long run before deciding to wear them during a marathon, you should also test out your fueling plan. So how exactly should you be fueling for those long, nearly-marathon length runs?  

marathon race

What to eat before a long run

Runs that are longer than an hour (not to mention two or three hours) require some preparation. When you run, your body relies on two forms of carbs for fuel– dietary carbs and glycogen (aka stored carbohydrates).

Glycogen stores are utilized in the first 30-60 minutes of running, then the body turns to any carbs from a recent meal that might be floating around in the body. That’s why eating carbs before a run is incredibly important. Starting a run with fully stocked glycogen stores sets you up for success.

While pre-run fueling will differ for each person, the general rule is to consume about 1 to 4 grams of carbohydrates per kilogram (0.4-1.8 grams of carbohydrates per pound) of body weight 1 to 4 hours before running. Obviously that’s a very wide range.

For a 150 pound runner, that can be anywhere from 60-270 grams of carbs. If you’re eating a few hours before a training run, consume a complete meal with carbs, protein and fat. You’ll likely be on the higher end of the range, especially if your run is in the double digit mile length. The further out you are from your run, the larger the meal you can consume.

runner on pavement

One hour before your run, aim to consume easy to digest carbohydrates, while keeping protein, fat, and fiber content low to avoid stomach upset. For example, the 150-pound runner may eat 1 slice of toast (13 g) with 2 tablespoons of peanut butter (7 g), 1 banana (27 g), and 1 tablespoon of honey (17 g). Some smaller carb-rich foods include fresh or dried fruit, pretzels, white bread, or a bar.  

Finally, make sure you are hydrating before your runs to prevent dehydration. Starting runs in a dehydrated state can negatively impact performance and make it feel like you are working extra hard!

While you should be hydrating with water, note that if you are a coffee drinker, you might feel encouraged by the fact that research has shown caffeine may benefit performance. However, if you do not typically drink coffee before running, marathon training runs are not the ideal time to start, as caffeine can cause an upset stomach.

What to eat during a long run

Perfecting the art of eating on the run may be one of the more difficult aspects of marathon training. If you’ve ever gone on a long run without fueling properly, you are likely familiar with the fatigue, brain fog, and heavy legs that can set in. Indeed, this occurs because after about 60-90 minutes, glycogen stores and dietary carbs are depleted.

For runs that are between 1 to 2.5 hours, aim to consume around 30-60 grams of carbohydrates per hour. For runs over 2.5 hours, it is recommended to consume around 60 grams of carbohydrates per hour. Some popular options include:

  • Gels such as Humagel (21 g carbs per packet), Genucan  (19 g per packet)
  • Chews such as Gatorade G Series 01 Prime Energy Chews Mixed 4 Pack (4 Sleeves)“>Gatorade Endurance Chews (31 g carbs per pack), or How to handle GI distress

    For those with sensitive stomachs, consuming a large amount of carbohydrates while running may seem daunting. That is why these pre-marathon long runs are so important, because they allow us to practice fueling strategies to see what works best. 

    If you find that you are constantly experiencing GI distress during your long runs, check that you are not consuming high amounts of fats or fiber before hitting the road. For plant-based eaters, certain foods like beans, lentils are high fiber fruits and veggies, may contribute to GI distress during a run. Use these swaps instead.

    If you feel like you’re too full on the run, start out with small amounts of carbohydrates and gradually increasing the quantity over time. Also, try out different carb sources. Some people find that sweet foods may not sit well in their stomach, so they opt for salty foods, like pretzels or bread.

    Additionally, some runners find that fructose, a sugar found in fruit and some sports drinks, causes GI upset. It helps to check the ingredients in your fuel of choice. If you find one particular brand gives you an upset stomach, you can always try another brand or type of fuel. Practice makes perfect!

    Hydrating on the run

    In addition to carbohydrates, it is also essential to adequately hydrate while running. Depending on weather conditions, aim to drink around 12-24 ounces per hour (think of 1 ounce as 1 gulp). You may need to drink even more if it’s hot or humid.

    Being properly hydrated will help prevent dehydration and delay fatigue. If you’re unsure if you are hydrating properly, try calculating your sweat rate to assess your hydration status.

    You might include a sports drink as well, which along with carbohydrates, will provide the electrolytes (sodium and potassium) that are lost in sweat. Sports drinks should not take the place of fuel, such as gels or food, as they typically contain fewer carbohydrates, but they can be a great addition. Be aware, however, that sports drinks cause some people GI upset due to fructose content, so be sure to try them before marathon day.

    runner in race

    What to eat after a long run

    You may have completed your long run, but your work is not yet done. Around 30-90 minutes after your run, consume carbohydrates and protein in about a 3:1 ratio to being the recovery process. Carbohydrates are necessary to replenish glycogen stores as well as to prevent muscle breakdown.

    If you do not get enough carbohydrates after a long and hard run, your body will break down other sources of fuel (such as protein, aka muscle). That will result in even more wear and tear on the muscles and may even cause soreness.

    In addition to carbohydrates, protein rebuilds and repairs muscles that worked hard during running. Some ideas for recovery protein might be a smoothie with fruit and protein powder, an oatmeal bowl with nuts and yogurt, or eggs or tofu with toast.

    Even if you drank during the run, make sure you hydrate after a run to replace the fluids lost in sweat. In addition to water, consider including a bit of salt as this will help your body retain water. This can be accomplished with sports drinks or by adding some salt to your food.

    By practicing your fueling on those long pre-marathon runs, you are one step closer to strong running and recovery.

    Tamar Kane is a dietetic intern with an MS in Nutrition and Exercise Physiology from Teachers College Columbia University. She lives in NYC and enjoys running, playing with her dog Roo, drinking coffee, and training her gut to handle coffee on runs.


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I’m Natalie Rizzo, an NYC-based Registered Dietitian.

My mission is to help everyday athletes fuel their fitness with plants.

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