What to eat before a half marathon, according to a sports dietitian

Preparing for a half marathon requires more than just physical training. I remember learning this the hard way when I ran my first half marathon in 2018. I paid no attention to my carbohydrate intake, electrolytes, or pre-race fueling, and boy, did I feel it. Without the proper glycogen stores needed before an endurance event, I “hit the wall” 6 miles into the half marathon. The second 7 miles was, to say the least, not fun. In 2018, I did not pay attention to what to eat before a half marathon to run my best race.

I have since dialed my long distance running nutrition. Being a registered dietitian, I’ve learned and tested thousands of times how exactly to fuel my and my client’s bodies with the right nutrients to optimize performance, have a high-quality pain-free race, and ensure there’s high enough energy levels to blow past the finish line.  

In this post, I will guide you through a comprehensive race nutrition plan for the week leading up to your half marathon, as well as specific recommendations for the day and night before your half marathon.

What to eat the week before a half marathon

When determining what to eat before a half marathon, stick to complex carbohydrates, vegetables, lean fats and proteins like the avocado bowl with egg and tomatoes.

What you eat in the days leading up to your big race matters a ton! Carbohydrate loading, also known as “carb loading”, studies show is one of the most important performance enhancing strategies used by half marathon runners and elite athletes alike.

Whether you’re preparing for a marathon or a half marathon, proper increased carbohydrate intake will provide you with energy you need to perform at your best on race day.

 Here are four the most important aspects of nutrition strategy the week before a half marathon:

  • Carbohydrate Loading
  • Consume high-quality protein
  • Opt for “healthy” fats
  • Hydration, hydration, hydration

Carbohydrate loading

The goal of carb loading is to maximize glycogen stores in the muscles and liver. Glycogen is the primary fuel sources during all exercise.

Muscle glycogen broken down to glucose in the body which then becomes a readily available energy source for activity.

Carb loading won’t make you run faster! That’s what your half marathon training is for. But, carb loading helps prevent athletes from bonking, or “hitting the wall”, during any endurance activity. 

Carb loading is a mandatory nutrition strategy for athletes participating in any events lasting longer than 90 minutes which includes the marathon and half marathon.

Carb loading is not necessary for shorter races like 5K or 10K. A 5K, on average, will take a runner 30 minutes and a 10K, on average, will take a runner 60 minutes. As glycogen reserves only run out after 90 minutes of activity, its unlikely your body will need to switch to fat reserves for energy during those race distances.

How should I carb load before a half marathon?

You should start carb loading 7 days before a marathon and 3 days before a half marathon.

Aim to consume around 7-10 grams of carbohydrate per kilogram of body weight per day during the carbo-loading phase.

For example, if you weigh 70 kilograms (or 154 pounds), you should aim for approximately 490-700 grams of carbs each day. For context, a cup of cooked pasta is between 37 and 43 grams of carbohydrates.

This is a lot more than people might expect. To hit the lowest threshold of carbohydrate intake during a carb load phase, you’d need to consume 10 cups of cooked pasta.

When consider what types of foods to include in your carb loading period, here are common food staples of the running community:

–   Sweet potatoes (27g per 1 cup)

–   Oatmeal (27g per 1 cup cooked)

–   Quinoa (39.4g per 1 cup cooked)

–   Rice (45g per 1 cup cooked)

–   Pasta (40g per 1 cup cooked)

–   Toast (13g per 1 slice wheat toasted)

–   Pancakes (8g per 1 oz of pancakes)

–   Bagel (48g per 1 bagel)

–   Bananas (27g per 1 banana)

–   Gatorade (36g per 100ml)

Even though you might be used to whole grains and complex carbohydrates, decrease excess fiber intake during the carbo loading phase. A high amount of fiber is difficult to digest and may irritate your gastrointestinal system.

Read our blog post to learn the ins and outs of safely carb loading.

Consult a Registered Dietitian to learn how adapt your carb loading meal plan if you have diabetes or need to watch your blood sugar levels. 

Eat high-quality protein

During the carb loading phase, 85-90% of your daily caloric intake will come from carbs.  This also means that you’ll be decreasing your low-carb vegetable, fat, and protein intake.

However, protein plays an important role in muscle repair, development and recovery.

Make sure your remaining calories include small amounts of protein.

As a registered dietitian, I recommend lean sources of organic proteins like chicken, turkey, fish, beans, lentils, and/or tofu in your meals to support your half marathon training and aid in muscle recovery before the race. 

Opt for healthy fats

Similarly, make a point to chose healthy fat choices the week before your half marathon.

Healthy fats in your meals to maintain a balanced diet like avocados, nuts, seeds, peanut butter, and olive oil.

Healthy fats are a highly-concentrated energy source (9 calories/gram) which is double that provided on average by carbohydrates and proteins. After the depletion of carbohydrates during exercise, the body will turn to oxidizing fat for energy.

Additionally, healthy fats contain vitamins A, D, E, and K which are fat-soluable and help with overall nutrition nutrient absorption by the body. And finally, healthy fats help regulate and with the production of testosterone and estrogen which enables muscle growth, metabolism and recovery.

Hydration, hydration, hydration

To stay hydrated – increase your consumption of fluids and electrolyte-filled sports drinks throughout the pre-race nutrition phase.

Gatorade is a great choice because it contains carbs and electrolytes. Electrolytes are important for replenishing sweat losses and preventing cramping.

What to eat the day before a half marathon

A Mexican inspired sweet potato bowl which is a recommended meal when determining what to eat for a half marathon.

The day before your race, increase your carbohydrate intake to 8 to 12 grams of carbs per kilogram of weight. This is the peak of your high carbohydrate diet.

While it’s popular to discuss the pre-race pasta dinner, part of the carb loading process means including high quantities of carbohydrates in your breakfast and lunch as well.

The best practice when determining what to eat before a half marathon – practice your day before nutrition before long training runs. Within a half marathon training plan, you’ll have long run distances of 10 to 12 miles which offer a perfect opportunity to experiment with how nutrition impacts your performance.

What to eat the night before a half marathon

The night before a half marathon, have a high-carb, low-fat meal that you’ve had before and is familiar to your digestive system.

Choose foods like as pasta, rice, bread, or potatoes as your main carbohydrate source.

Avoid heavy, fatty, or high-fiber foods. Alfredo pasta is an example of a high fat meal that probably won’t sit well!

Before bed, eat a small carb snack the night before your race like some graham crackers or pretzels for extra carbs. Again, limit fat and fiber.

As mentioned above, gradually increase your carbohydrate intake in the days leading up to your race. Don’t bank on one meal the night before to be enough.

What to eat during your half marathon

If you’re also interested in what to eat during your half marathon, consult our detailed blog post.


How should I eat the morning of a half marathon?

Eat easily digestible carbohydrates that won’t cause discomfort during the race. Avoid high fat foods like bacon, sausages, and cheeses on race morning.  If your breakfast is 4 hours before the race, have 4 grams of carbs in your pre-run meal per kg of body weight. If your breakfast is 3 hours before the race start, have 3 grams of carbs per kg. If your breakfast is 2 hours before the race, have 2 grams of carbs per kg. And lastly, if your breakfast is 1 hour before the race, have 1 gram of carbs per kg. Then, take one or two energy gels or chews to the starting line.

How should I eat the night before a half marathon?

The night before a half marathon, have a high-carb, low-fat meal that is familiar to your digestive system. Choose easily digestible foods such as pasta, rice, or potatoes as your main carbohydrate source.

Do you need to eat before a half marathon?

Most half marathon starts are early in the morning, so I totally get it if you’re not hungry for a big pre-race breakfast at 5am. But you should eat a pre-race meal or snack regardless.
Choose easily digestible carbohydrates that won’t sit heavily in your stomach. Opt for things like a banana, a small energy bar, a piece of toast with jam, or a few handfuls of dry cereal or granola at the very least. 

What not to do the day before a half marathon?

The day before a half marathon is time for rest, recovery, and mental preparation. Avoid intense exercise and training sessions the day before your race because they will leave you fatigued. Stick to light, low-impact activities such as a short, easy jog or a relaxed walk to keep your muscles loose without pushing yourself too hard. Stick to your marathon training plan. You should also avoid alcohol, trying new foods or supplements, having a late night, and dehydration.

What to eat after a half marathon?

First things first, start by rehydrating your body with fluids and electrolytes. Drink juice or a sports drink to replenish the fluids lost during the race. Aim to drink enough to satisfy your thirst, while taking small sips. Avoid chugging plain water as this will cause your blood sodium levels to drop, causing exercise-associated hyponatremia (EAH). LMNT or Nuun sports drinks are good choices to avoid EAH. 
Your post-race meal should be eaten within 30-60 minutes of finishing your race. This window of time is when your body is most receptive to nutrient absorption and muscle recovery. A solid post-race meal to refuel includes carbohydrates, lean proteins, and antioxidants. Examples are grilled chicken with brown rice and steamed vegetables or a tofu stir-fry with quinoa and mixed greens.

0 comments… add one

Leave a Comment