Training for a marathon is a whole body commitment that requires a full lifestyle makeover. You’ll not only be tackling intensive training sessions on and off the trails, but also giving your diet an overhaul.

Preparing your body with proper nutrition is almost as important as logging miles on trails and treadmills. Proper nutrition will help you get your body in peak health leading up to race day. We’ll show you how to optimize your energy levels and run times by eating the right foods, and the right time.

The Key Nutritional Components of Marathon Training

First, let’s look at the necessary components of nutrition for a healthy run.


As if you needed an excuse to up your carb intake. When it comes to marathon training, carbohydrates are your best friend. Carbs provide your muscles’ primary source of energy and should be the core of your training diet.

Carbohydrates are broken down by your body into glucose (or sugar) and stored in your muscles and liver as glycogen. Glycogen serves as the primary energy source for our muscles. So why are carbs so often seen as dietary enemies? Simply put, when you aren’t burning carbs as fuel for fitness, the glucose that isn’t being used by your muscles can be stored as fat. Limiting carbs can be healthy for sedentary lifestyles, but when you’re training for a marathon, it’s time to carb up.

Have you ever been running and “hit the wall,” where you feel you can’t go another step further? That’s the feeling of your glycogen storage hitting empty. To ensure you’re giving your body the energy you need to succeed, runners should be consuming between 2.5–3.5 grams of carbohydrates per pound of body weight while training. During the week of your race, begin increasing this amount slightly to increase your glycogen storage. Aim to be consuming about 4.5 grams of carbs per pound of body weight two to four days before your marathon to maximize energy.


Lean protein is also essential to your run training, as it helps your body build and repair damaged muscles. But before you load up on steak, it’s important to note that a recent study of the US population’s dietary habits show that many Americans (mainly men) are actually consuming more chicken, beef and egg protein than recommended. Increasing plant proteins and getting the recommended 2 servings of fish protein per week is a great way to find balance.

Because protein slows down digestion, it’s best to consume the majority of your protein after you’ve trained for the day. Stick to only a few grams pre-run and save the lean meats and plant proteins for later in the day.


Keep your body hydrated all day, not just while you’re running. Training outdoors in the spring and summer sunshine is lovely, but don’t forget that the warmer weather will impact your hydration as you sweat more. Account for this by upping your water and electrolyte intake on hot days.

If you’re feeling thirsty, you’re already dehydrated.

Track your hydration levels throughout the day by checking your urine—if you’re well hydrated, it will be pale yellow, like lemonade. If it’s darker (think apple juice), you need to up your water intake.


Sweating doesn’t just cause us to lose fluids, it also depletes our electrolyte storage. Sodium is the most important electrolyte you’ll lose during your run. Sodium helps runners by easing muscle contractions and cramps, and maintaining fluid stores.

Sports drinks are a source of sodium, potassium and other vital electrolytes, but if you’re marathon training in hot weather, you may need to further supplement with 400–800 mg of sodium in the form of salt or electrolyte tabs in your water or sports drink.

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What to Eat and When


Maintain hydration by drinking 12–20 ounces of water upon waking. Drink 6–10 ounces more before the start of your run. If you’re training later in the day, maintain a consistent level of hydration.

Pre-run meals and snacks should be higher in carbs (about 70%) to boost your energy levels during training. Time your meals for 2–3 before your training session if possible, or supplement with a small snack 1–2 hours before your run.

“Pre-run snacks should be made up of easily digestible carbs, and should be low in fiber, fat, and protein,” says Isabel Smith, a Registered Dietitian. “This provides fuel while preventing cramping or stomach upset.”

Here are some high carb snacks to get you started:

  • Greek yogurt topped with berries
  • Crackers with hummus
  • Whole wheat toast with almond butter and an apple  
  • Banana slices with peanut butter

During the Run

Stick to just water if your training session will be an hour or less. Aim to consume about 6–8 ounces of water every 15 minutes to stay hydrated while preventing fluids from sloshing around while you run.

For runs over an hour, supplement with an extra 30–80 grams of carbohydrates per hour. An easy way to get a carb boost on the go is in the form of sports gels or bars or sports drinks. “Sports drinks provide fluid, electrolytes, and easy to digest carbs,” says Smith. “Try different foods and drinks during your training to see what works best for you. What one person feels good with doesn’t always work for another.”


Immediately following your run, it’s time to rehydrate. Do you know your sweat-rate per hour? You can find out how much fluids you’re losing during a run by weighing yourself immediately before and after training. Consume about 20 ounces of fluid for every pound of fluid lost during your run.

Consume a snack within 30 to 60 minutes post-run, or time your next meal for this time. A good post-run recovery meal should provide a mix of carbs and lean proteins. Carbs will replenish your energy levels, while protein helps your body repair muscle tissue. Most people need between 10–25 grams of protein and 60–100 grams of carbs to feel their best. If you have a hard time stomaching a snack that soon after exercising, consider a liquid boost like a smoothie.

Here are some balanced recovery snacks to try:

  • Peanut butter and banana sandwich on whole wheat bread with a ½ cup of cottage cheese
  • Greek yogurt with 1 cup of fruit and 1 tsp of honey
  • Turkey and cheese sandwich on whole wheat bread with an apple
  • Sports drink (16 ounces) with 6 ounces of cottage cheese

Finding What Works

Don’t forget: every body is unique! Your marathon training nutrition plan will depend on what works best for you. The training phase is perfect for testing different nutrition and hydration strategies to find out what makes you feel the most energetic. On the last days leading up to your race, it’s best to stick with familiar foods and strategies so your stomach won’t be contending with anything new or unfamiliar.

Are you ready to hit the trail to begin marathon training? What is your go-to training snack or meal? We’d love to hear about it in the comment section.