Nutrition Guidelines for Ultrarunning

Before we start, I have to tell you that I am not a dietician or registered nutritionist. However, I have run tens of thousands of miles during my career, and I’ve learned a lot along the way about how to fuel myself for ultrarunning. Of course, I made lots of mistakes along the way, too! Mistakes I hope I can help you avoid.

So, let us look at general nutrition guidelines; the 60/20/20 split and a closer look at carbohydrate, fat, and protein intake.

General Nutrition Guidelines
These general principals should guide your overall approach.

  • Aim for fitness.
  • Aim for a healthy weight.
  • Be physically active each day.

To build a healthy base, you should:

  • Choose sensibly.
  • Eat a healthy diet composed of real foods.
  • Eat a variety of grains, especially whole grains.
  • Eat a variety of fruits and vegetables daily.
  • Moderate your saturated fat and cholesterol intake.
  • Moderate your salt intake.
  • Moderate your total fat intake.
  • Moderate your sugar intake.
  • Moderate your alcohol consumption.

In the U.S., government guidelines say that your total calorie intake should be between 1,600 to 2,200 calories per day. These guidelines are great for the typical, inactive American. However, if you are a very active athlete doing 60 to 120 minutes of purposeful exercise every day, use the following calculation to determine what your daily caloric intake should be.

Body weight x 21 to 25 calories per pound of body weight

As an example, if you weigh 150 pounds, you need to consume 3,150 to 3,750 calories a day.

The 60/20/20 Split
A healthy diet includes carbohydrates, fat, and protein in a healthy balance. As a general rule, your calorie intake should be:

  • 60 percent carbohydrates
  • 20 percent fat
  • 20 percent protein

Carbohydrates: The First Source of Fuel

Carbohydrates should account for about 60 percent of your total calories.

Carbohydrates provide glycogen which is your primary fuel source. Most glycogen is stored in the liver, with some stored in muscle tissue. While glycogen is your primary fuel source, your liver can store a maximum of 1,800 to 2,000 calories, which is only enough to fuel you for 90 to 120 minutes of vigorous activity. So, if you try to go out and run for 3 hours without taking in any calories, you are likely to “bonk” – which is another way of saying you have a low blood glucose level, or low blood sugar. So, to restore your glycogen stores you must ingest carb-rich foods and beverages before, during, and after a training run or race.

When you are training, consume 3 to 4 grams of carbs per pound of body weight (or 450 to 600 grams of carbs for a 150 pound athlete). Before a race, you may want to do “carb loading” for 3 to 4 days before the event. To do this, increase your intake to 4 to 5 grams of carbs per pound of body weight.

Within 15 to 30 minutes after a training run or race, refuel! This 15 to 20 minute window is when your muscles are the most receptive to replacing glycogen. To refuel, consume 0.50 grams of carbs per pound of body weight within 30 minutes.

Fat as Long-Term Fuel
Approximately 20 percent of your calorie intake should be from fat.

You need fat as fuel for ultrarunning. Fat is your most concentrated source of energy. In fact, fat has more than twice as much potential energy as carbohydrates.

While glycogen stores in the liver can only supply a maximum of 1,800 to 2,000 calories, fat stores can supply up to 100,000 calories! That is enough for over 100 hours of marathon running. The key is to train your body to burn fat so that you can effectively use it as an important fuel source as distance or time increases (you can accomplish this by doing your long training days, as described in last week’s “Pace Yourself” tips).

When you are training or racing, consume approximately 0.50 grams of fat per pound of body weight (or 75 grams of fat for a 150 pound athlete). Fat is not a quick source of energy; it takes 3 to 4 hours for the energy in fat to be released into your system, so is very useful when you plan to be on the move all day.

Protein Needs
Protein should account for at least 20 percent of your total caloric intake.

Protein is critical for:

  • Building, maintain, and repairing muscles
  • Making hemoglobin, to carry oxygen
  • Forming antibodies
  • Providing your body with its “final” fuel source

Endurance athletes can not live on carbs alone. While protein supplies 5 to 15 percent of the body’s need for energy, mostly to build, maintain, and repair body tissue, your body does not maintain a store of protein for use as energy. So, you need to replace the protein your body is using during training and racing.

When you are training, consume approximately 0.55 to 0.75 grams of protein per pound of body weight (or 95 grams of protein for a 150 pound athlete). If you are training a lot you may need to increase your protein intake to 0.80 to 0.90 grams per pound in order meet the needs of your body tissue, especially muscle!

On race day, protein will provide energy at the late stages of the race. So, be sure to eat foods that provide protein. You might want to try Mucle Milk or Ensure (with extra protein) as liquid sources of protien. After a race, consume protein-rich foods at your next meal to refuel and promote rebuilding of muscle tissue.

Nutrition for Race Day

In addition to the specific guidelines about carbohydrates, fat, and proteins above, on race day remember: it is a simple matter of “calories in, calories out.” As a general guideline, eat 100 calories per mile or 300 calories per hour. Consume an additional 100 calories per 1,000 feet elevation gain. This may all seem complicated, but I always advise my clients to simply:

Listen to your body and
eat what you crave!


Your body is smarter than you are and will tell you what you need. But you have to learn to listen to it. Remember to eat a balance of carbohydrates (simple sugars), proteins, and fats. Use the aid stations and, if you have crew, make sure they have a range of foods to give you. Sometimes it is easier to get your calories from liquid sources (like Ensure) or energy gels during a race. Try these during your pre-race training and see what works for you. Of course, stay hydrated, and don’t forget to take in electrolytes, including sodium!

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