Training for an Ultra or Marathon? Here’s Everything You Need to Know About Your Diet
Sports dietitians explain how crucial it is to nail your nutrition strategy — plus exactly how to do that.
Nutrition, much like recovery, is an oft-overlooked part of marathon or ultra training. In the short and long terms, that can be detrimental to achieving performance goals and, in some cases, can negatively affect overall health.
Understanding the ins and outs of a marathon training diet is a huge missing piece of the training puzzle, says sports dietitian Roxana Ehsani.
“Runners are so focused on their training mileage each week, they often overlook fueling,” she says. “But nutrition is so critical during training because you’re providing your body with fuel so you can keep going, and complete those training runs.”
To help, we spoke with several dietitians who specialise in sports and endurance nutrition to break down what runners need to know about a marathon training diet.
Why Nutrition Is So Important During Marathon Training
The analogy is simple: Your body is a car. If a car runs out of gas or electric charge, it’s going to stop working. If your body runs out of fuel — energy from calories — it’s going to pull off the road, sit down on the curb, and cry.
As your weekly mileage and intensity increase, your caloric needs increase (more on that in a minute). If you’re properly fueling your body throughout the training cycle, you’ll see fitness and performance improvements, and when it’s time to ask your body to push during marathon race day, it’ll respond.
The catch: You need to practice your fueling so you learn what your body can tolerate and what will give you the energy to push forward. That’s because some foods may not actually settle well when you eat them before a run, sending you straight to the bathroom and making those long kilometres all the more difficult. You may also want to play around with timing and the amount of food you eat.
“Just like your runs train your muscles to run 42.2 kilometres, practicing your fueling trains your GI tract to digest food,” says Kristy Baumann, dietitian and marathoner. “The cool thing is that your stomach is a muscle. It can be trained.”
This means you want to try out different pre-run meals and snacks — the night before and the morning of key workouts — to see what sits well.
In addition to what you eat before a run, mid-run fueling for long runs and on race day is critical to making it through double-digit kilometres.
Running inherently causes some GI distress because of the jostling and the fact that blood is pulled away from the GI tract to be used in the muscles for physical activity, Ehsani explains. When you start eating foods or fuel like gels or chews during a run, that can cause further distress until your body gets used to working with it.
When it comes to actually fueling during a long run (the experts Runner’s World spoke with say that’s for runs that are 70 minutes or more) and on race day, you want to aim for 50 grams to 90 grams of carbohydrates per hour, Baumann says. While the common guidance for runs up to two hours is 30 grams to 60 grams of carbohydrates per hour, this will not be enough for the marathon distance, particularly for runners who are on the course for 3.5 hours or more, Baumann says.
Baumann refers to a 2019 paper published in Nutrients, which says for events lasting more than 2.5 hours, athletes should take in 60 t0 70 grams of carbohydrate per hour, and “if tolerable,” up to 90 grams per hour. These amounts have been associated with improved performance.
“Part of the training process involves training your stomach to meet your carb intake goals,” Baumann says. “This is a piece of the puzzle that many runners fail to do, and they question why they hit the hall on race day when it never happened during training.”
She also reminds runners that it’s crucial to fuel early and often — it takes about 15 to 20 minutes for your body to be able to use that energy after consumption. So, if you wait until your muscles are already in need of energy and then you tack on 20 minutes for your body to absorb that energy, you are likely looking at a bonk.
How to Figure Out Your Caloric Needs for Long Runs
That said, both experts point to a few different equations that can help people determine how many calories they need as a baseline, or as Baumann calls it, “everyday nutrition.”
Scientifically, this is called your basal metabolic rate (BMR) or the resting metabolic rate. It determines how much energy our bodies need just to survive.
One calculator uses the popular Mifflin-St. Jeor equation. It looks at baseline factors, including weight, height, age, and sex. (This is the same formula used in the calculator below.)
“You also have to account for how active you are on a daily basis,” Baumann says, which includes structured physical activity like your marathon training plan, and non-exercise activity like walking to the bus stop, brushing your teeth, or chasing a toddler down the driveway.
To do this, you’ll multiply your BMR by an activity factor, which varies from 1.0 to 2.5. Baumann says someone who is training for a marathon will use at least a factor of 1.55, assuming she’s working a desk job, and training for 30 to 60 minutes a day, five days a week. “The factor increases from there based on the volume and intensity of training, and how active a person is at their job and the rest of the day outside of training,” she says.
In the calculator below, you’ll get the 1.55 multiplication by choosing “moderately active” for the last question regarding your activity level and that corresponds to 30 to 60 minutes of exercise, five days a week when working a desk job. That also means as you work through marathon training, and you reach higher activity levels — “active” and “very active” in the calculator below — you’ll see your calorie needs go up.
Baumann says she often sees endurance runners consider their baseline caloric needs and then add on their marathon training needs. But they’re forgetting the calories needed for their everyday activity, like walking their kids to the bus stop, lifting boxes at work, climbing stairs with a load of laundry. “This can lead to underfueling,” she says.
A telltale sign of not eating enough is injury. “A lot of runners don’t realise that if we’re underfueling, we’re setting ourselves up for injury,” Ehsani says. That’s because your body does not have enough calories to fuel performance and recovery on top of its daily systems. Underfueling can also lead to a weakened immune system and a poor mental state, she adds.
Baumman says that not consuming enough calories can result in fatigue even if you’re well-rested. “Or your fitness may not be improving even though you’re putting in the hard work,” she adds. You might also feel hungry all of the time if you’re underfueling.
Overfueling can also be a problem. The first sign might be unexplained weight gain, Baumann says. In some cases, muscle gain can contribute to weight gain, but overfueling will contribute to increased fat mass, she says. “It can be tricky to differentiate,” she says, noting that most people don’t have access to body composition labs (and most body scan machines in gyms are inaccurate).
Aside from unexplained weight gain, runners who are overfueling might also feel sluggish versus the fatigue you’ll feel from not eating enough.
A general breakdown of these nutrients looks something like this, Ehsani says:
- Carbohydrates, the body’s preferred source of fuel, especially for distance running, should comprise about 60 percent of daily calories. Some people might bring their carbohydrates down to 55 percent, but Ehsani cautions against dropping anymore than that when you’re running consistently.
- Protein and fat are roughly the same at about 20 percent.
🍽️ The Role of Carbs in Running
WHY YOU NEED THEM: Although carbohydrates have gotten — and still continue to get — a bad rap, Ehsani says you simply cannot run without consuming them.
“These foods should be on our plates at every meal,” she says. “Carbohydrates are essential for giving the body energy. They provide the brain and the muscles with their preferred source of energy.”
When we consume enough carbohydrates, it prevents the body from tapping into our muscle stores for energy, ultimately preserving lean muscle mass, Ehsani explains.
WHERE TO FIND THEM: You’ll find this macro in a variety of foods, including whole grains, beans, rice, lentils and legumes, fruits, vegetables, and dairy.
ABOUT HOW MUCH TO HAVE: Baumann advises her athletes to consume roughly 7 grams to 10 grams of carbohydrates per pound of bodyweight per day — the lower end when you have a run lasting roughly an hour long and the higher amount for longer runs, ranging from two to 2.5 hours.
For example, a 68-kilogram runner who’s consuming 8 grams of carbohydrate per kilogram of bodyweight needs about 544 grams of carbohydrate per day.
A carb-rich breakfast — about 90 minutes to two hours before a long run — might look like: Oatmeal (1.5 cup old-fashioned oats), made with a ½ cup of 2% milk, topped with a banana, ½ cup of blueberries, a tablespoon of honey, plus two slices of whole wheat toast topped with a tablespoon of almond butter. That offers up nearly 180 total grams of carbs.
Runners know that after a workout, protein is king. And it is, but so are carbohydrates. Experts recommend refueling with a meal or snack that has a 3:1 carbohydrate-to-protein ratio; a glass of chocolate milk has this perfect ratio. Not only will the protein help your muscles repair all of those micro-tears from the workout, the carbohydrates will replenish the glycogen stores in the muscles, which they need to move.
🍽️ The Role of Protein in Running
WHY YOU NEED IT: Running causes microtears in muscles throughout the body, and it’s protein that will rebuild and repair them to keep you moving — and getting stronger.
Baumann talks about the importance of timing your protein consumption correctly, particularly jumpstarting your day with this macro. The body can only use about 20 grams at a time; it can’t be stored like carbohydrates or fat, so anything extra won’t speed your recovery or result in stellar gains, if you will. That means you’ll want to consume protein throughout the day to maximise its benefit. Miss it in the morning, and you risk not meeting your daily needs.
Consuming too much protein at once can also fill you up to the point at which you’re not going to be able to eat the amount of carbohydrates you need to fuel your marathon training runs.
WHERE TO FIND IT: Your best sources of complete protein — which includes all nine essential amino acids — include dairy, eggs, meat, and soy.
Plant-based foods like rice and beans, whole grains, nuts and seeds, and some vegetables contain incomplete proteins. But when you eat a varied diet, those incomplete proteins join forces to form complete proteins.
Complete proteins are not inherently better than incomplete proteins, but your body can’t build muscle or repair muscle without all nine essential amino acids.
ABOUT HOW MUCH TO HAVE: For athletes, like runners, experts recommend consuming 1.75 grams to 2.8 grams per pound of bodyweight per day. It’s not surprising that the International Association of Athletics Federations (IAAF) released a statement back in 2019 saying athletes need more protein than the average person (even up to 3.5 grams per pound of bodyweight). After all, runners are building and repairing more lean muscle and they need more calories to support their training.
A breakfast with 20 grams of protein might look like: 1 cup of Greek yogurt topped with a tablespoon of honey, berries, and granola; or two scrambled eggs mixed with a splash of milk and shredded cheese, topped with veggies and black beans.
Within 30 to 60 minutes of finishing a run, you’ll want at least 20 grams of protein to kickstart recovery.
For example, try 1 cup of cottage cheese with a handful of whole-grain crackers or a glass of chocolate milk with a piece of toast topped with 2 tablespoons of peanut butter.
🍽️ The Role of Fat in Running
WHY YOU NEED IT: Fat is crucial for hormone production, vitamin and mineral absorption, and fighting inflammation (which plagues every runner, and can depress the immune system, cause aches and pains, and even contribute to chronic illness, like cardiovascular disease and diabetes). Plus, it tastes good.
WHERE TO FIND IT: Healthy-for-you fats are polyunsaturated and unsaturated, found in olive and nut oils, nuts and seeds, fish, and avocados. Ehsani specifically calls out the importance of omega-3 fatty acids found in these food sources, which help fight inflammation and promote brain health.
ABOUT HOW MUCH TO HAVE: For active adults, Ehsani says the minimum fat requirement is 60 grams per day or roughly 20 to 35 percent of daily calories. But go easy before you head out for workout. Like protein, fat slows digestion, which means consuming a fat-heavy meal (even good-for-you fats) before you start moving can cause GI distress.
Important Micronutrients for Marathon Training
Beyond the big three — carbohydrates, protein, and fat — marathoners need to pay attention to micronutrients to support their training, recovery, and overall health. These vitamins and minerals not only provide nutrients, they often help the body absorb other micro and macronutrients, Ehsani says.
There’s a reason nutrition buffs tell us to “eat the rainbow.” That’s because when you eat all the colors you’re getting a wide variety of micronutrients. For example, orange-colored produce like carrots is high in beta carotene, which converts into vitamin A. Dark green produce, like spinach and bok choy, gets its color from folate, a water-soluble B vitamin.
“It’s a good idea to get blood work done at least once a year to make sure you have optimal levels of your nutrients,” Ehsani says. Specifically, she recommends testing ferritin and vitamin D levels and getting a complete blood count and comprehensive metabolic panel.
Iron
Iron is king when it comes to moving more, because it helps make hemoglobin, a protein in red blood cells — and red blood cells move oxygen around the body.
How Hydration Needs Change During Marathon Training
Things runners love: running. Things runners do not love: strength training, running slow enough on easy days, and hydrating. But dehydration, Ehsani says, happens easily and can negatively affect performance in the best case, and overall health in the worst case.
“Most athletes come to practice in a depleted or dehydrated state,” she says. And that’s before they put in the work.
Knowing how much to hydrate, or specifically, how much water you need, is tricky. A good rule of thumb, Ehsani says, is to divide your weight in half to give you a rough amount of fluids you need in ounces.
After a hot and humid run, you’ll want to rehydrate with about 1-1.5 litres of water per kilogram lost. So weigh yourself before and after your run to determine those kilograms lost.
There are other, more straightforward ways to determine if you’re drinking enough fluids (both water and electrolytes):
- How often you’re urinating → it should be every two to four hours
- The color of your urine → light lemonade is an indicator you’re hydrated; dark apple juice means you’re dehydrated
- How much you’re urinating → if your output is just a little bit, you’re probably dehydrated
“Drinking a cup of sports drink with electrolytes can help your body hold onto fluids better,” Ehsani says.
Without proper hydration, marathon runners can experience fatigue, nausea, GI distress, and decreased performance, Baumann says.
Before a run, particularly a long run, the rule of thumb, Ehsani says, is to drink 400 to 700 ml of water two hours before you head out and another 250 to 400 ml about 15 minutes before. But you can’t cram your hydration. ”You need to be drinking all day long to be hydrated,” she says.
While you’re on a long run, especially in the warmer months, Ehsani recommends drinking 6 to 12 ounces of water every 15 minutes, paired with carbohydrates and electrolytes. That might look like taking water with a gel and adding a sports drink to your water bottle; gels don’t typically contain enough electrolytes to be your sole source during a workout.
When choosing fuel or hydration with electrolytes, sodium is crucial because it’s the one that’s primarily lost in sweat, Ehsani explains. Aim for 200 to 600 milligrams per hour — less if you’re not a heavy sweater and more if you are. Sodium actually stimulates runners to drink more, it improves the taste, reduces urination to help maintain blood volume (keep you hydrated!) and is a key part of fully rehydrating runners.
Try These Meal and Snacks
Our experts have helped marathoners take the guesswork out of planning your marathon training meals — at least some of it.
Generally speaking, you’ll want your pre-run snacks and meals to be high in simple sugars (white bread or bagel, banana, pretzels) and low in fat, fiber, and protein, which can affect digestion and cause mid-run GI distress. And your post-run food should lean heavily on carbohydrates and protein.
Breakfasts
🕰️ 45 to 60 minutes before
Mid-morning Snack
- String cheese with whole grain crackers
Lunch
Mid-afternoon Snack
Dinner
Evening Snack
- Tart cherry juice with rice cake and nut butter
Anytime Pre-run Snack
🕰️ 30 minutes before
- Banana
- Slice of toast with a tablespoon of peanut butter
- Bowl of cereal with your choice of milk
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