Nutrition & Hydration for Marathon Training


Nutrition & Hydration for Marathon Training

Posted By By Meghan Hennessy, DPT


Preparing for a marathon involves more than just getting your miles in. Nutrition and hydration is equally as important during training as long runs so that your body is fueled and ready through all 26.2 miles. Coming up with a nutrition plan can seem like an arduous task, but by breaking it down to the basics and answering some common questions, we hope to set marathon runners up for success.

First, understanding the basics of nutrition is essential to creating a diet plan that works for you.

Understanding how glucose and glycogen work within your body is important.


  • Glucose (carbohydrate) is the body’s most readily available form of energy.
  • Glucose can be derived from your body’s stores of glycogen or dietary intake.
  • Glycogen is stored in muscle and the liver. The body can only store a limited amount. It is typically depleted by the end of 2 hours of exercise. As a result, longer runs require additional glucose supplementation to fuel the muscles and organs.

With this in mind, we can answer some common questions on nutrition.

While training for a marathon, what should I be eating daily?


  • When training for an endurance event, your body is continually in a state of preparation as well as recovery.
  • The key to balancing both is maintaining adequate glycogen (carbohydrate) stores.
  • In general, you want to take in enough carbohydrates to restore glycogen, protein to rebuild muscle and healthy fats to support neurologic recovery.
  • The American College of Sports Medicine recommends that 30-50% of your total daily calories come from carbohydrates (higher during heavy training days/lower during recovery) and 25-30% come from fats.
    • For endurance athletes, the recommended daily allowance of nutrients is different than for sedentary individuals and even strength athletes.  Endurance athletes should aim for 4-6g/lb of high-quality carbohydrates, 0.8-1.0g/lb of protein, 0.4-0.6g/lb of healthy fats per day.
  • Protein intake should be spread throughout the day, including before bed (Casein is best).

How are men’s and women’s needs different?


  • Women use less glycogen during training and cannot glycogen load to the same extent as men
  • Women oxidize less carbohydrates and more lipids during training
  • Women need fewer carbohydrates than men
  • Women require more protein/lb to maximize muscle growth

What should I eat while I run?


  • You should aim to replete about 200 calories per hour for runs lasting more than 1 hour (personally, I consume a few chews for anything over 30 minutes)
  • Carbohydrate is the fastest source of glucose
  • Fat and protein can slow down the digestion of carbohydrates.
  • Carbohydrates can be obtained from gels, chews, drinks, bars or real food such as fruit. There are many types of energy foods on the market and everyone’s GI tracts respond to each product differently. Your best bet is to try out several different products during training so that you have your preferred fueling source dialed in by race day.
  • Fruit is a natural way to obtain carbohydrates, but the fructose (fruit sugar) in fruit requires an additional step in metabolism to be broken down to glucose so is slower to be converted to glucose; this may cause GI upset for some.

What should I eat after I run?


The first 30–120 minutes

  • This is your time to optimize glycogen repletion. Women have a shorter window, with men closer to 2 hours.
  • For women a 2:1 carb:protein ratio is recommended, 4:1 for men. Recommendations are variable but mostly focus on men’s recovery needs.

4 hours after

  • 1.0–1.2g/kg/hour is consumed for the first 4 hours, followed by resumption of daily carbohydrate requirements.

Examples of Nutritious Fueling


  • Carbohydrates:
    • Whole grains
    • Quinoa
    • Fruit (fresh and dried)
    • Potatoes
    • Beans
    • Oats
  • Protein:
    • Whey protein (20g-40g) is best but pea protein is a great alternative
    • Lean meat
    • Fish
    • Dairy
    • Poultry
    •  Soy
  • Electrolytes
    • Sports drinks
    • Coconut water
    • Leafy greens
    • Dairy products
  • Anti-inflammatory foods
    • Salmon / fatty fish
    • Flaxseed
    • Nuts

How should I hydrate during training runs?


  • The American College of Sports Medicine (ACSM) recommends drinking two 8-ounce glasses of water or sports beverage exactly two hours before so that the fluids can be absorbed by the body.
  • O’Neal et al. 2011, describe the importance of utilizing sports beverages, as they are superior to water in meeting hydration needs.
  • ACSM recommends drinking 5 to 12 ounces of fluids every 15 to 20 minutes.
  • It is important to highlight that accomplishing the latter may be difficult and can result in overhydration if your sweat loss is too low.

Why are sports beverages better than water during marathon training?


  • For exercise lasting greater than 2 hours or for people with high sweat rates, it is important to hydrate with a solution that includes sodium. We lose sodium when we sweat. If not repleted, sodium loss from sweat can lead to dangerously low levels of sodium in the blood. We need sodium for heart, brain and muscle function.
  • Most commercially available electrolyte drinks like Gatorade or Powerade contain sodium. Gatorade Endurance Formula contains an even higher level of sodium and is geared toward endurance sports. There are other boutique-type drink mixes that contain varying combinations of electrolytes and carbohydrates.

How should I hydrate during the rest of the day when I’m not running?


  • It is important to replete any fluid lost during your runs. A simple and effective method is to weigh yourself before and after running. For every 1 kg (2.2 lb) of weight loss, 1L of fluid is needed. Researchers recommend repleting your fluid stores slowly within 2 hours of finishing exercise, up to 150% of the weight lost.
  • Daily hydration needs are just as important as race-day. For healthy individuals, Harvard Medical School recommends about 15.5 cups of water for men and 11.5 cups for women.
  • Other fluid sources (fruits, tea, etc.) may contribute to this total so an individual may only need about four to six cups of plain water.
  • The Centers for Disease Control and Prevention advises that plain water consumption does vary amongst age, race/ethnicity and socioeconomic status.

With that being said, it will be important for you to educate yourself on the above parameters and develop an individualized hydration strategy. By properly fueling and hydrating during training, you will set yourself up for success and may even avoid that mile 20 bonk!

By understanding your body’s needs and how it uses the food you feed it, you can start to build a nutrition plan that works for your lifestyle. All individuals' needs are different, so consult your healthcare provider before making any drastic changes to your diet.

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