Endurance Athlete Diet: What to Eat for Optimal Performance

Whether you're an endurance athlete or just want to improve your ability to exercise longer, knowing about basic nutrition is the first step. Eating the right foods in the right amounts helps provide the energy needed during endurance training. Learn how to maximize your athletic performance by adjusting your nutrition plan and leave your competition behind.

What Is Endurance?

Any aerobic exercise lasting one hour or more counts as an endurance activity. The most popular endurance events include running, swimming, and cycling. These may be single-activity events such as ultra runs, or multi-sport events like triathlons.

It takes a lot of energy to power through endurance events. This energy comes in the form of nutrition. Getting the proper nutrition for endurance (and energy) is important whether you are an elite or recreational athlete.

No One-Size-Fits-All Diet for Improved Endurance

Events vary, as do athletes and your everyday personal training clients. So, it should be no surprise that an endurance diet is not a one-size-fits-all solution. Factors to consider include body weight, environmental conditions, and nutrient timing, just to name a few. 

Each client will have different needs for different events. Finding the best solution may involve starting with basic nutrition recommendations. If they don’t supply the desired results, modify them as needed. Finding the best diet for endurance is often a trial-and-error process. 

As always, keep your scope of practice in mind as a personal trainer—make sure you're cleared to talk about nutrition with clients. Now, let's dig into the details of dietary needs for endurance.

Endurance Athlete Macronutrient Needs

Macronutrients are the basic components of the food we eat. These are carbohydrates, protein, and fat. 

Eating macros in proper ratios fuel your endurance. Healthy adult eating includes ratios of:

• 45-65% of calories from carbs

• 20-35% of calories from fat

• 10-35% of calories from protein 

Adjust these ratios based on the goal of the physical activity. For example, an endurance athlete would increase their carb percentage to improve muscle glycogen stores. A strength athlete would consume a higher protein intake. This would better support building more muscle mass.

How Many Carbohydrates Should Endurance Athletes Eat?

Carbs come in different forms. Two to know are simple and complex carbs.

• Simple carbs, also known as simple sugars, have one to two sugar molecules. These include glucose, dextrose, or fructose. Simple carbs break down quickly in the body. Foods with simple sugars include fruits, milk, vegetables, table sugar, candy, and soft drinks. They supply energy but lack fiber, vitamins, and other key nutrients.

• Complex carbs have three or more sugar molecules. You'll find these in foods like beans, whole grains, whole-wheat pasta, potatoes, corn, and legumes.

So, which kind of carbohydrate should you consume? Most carbs should come from complex sources and naturally occurring sugars. Processed carbs and refined sugars should be limited or avoided.

How many carbs should endurance athletes eat? There will be some differences based on the type and duration of training. The general rule is to increase carbohydrate intake by up to 70% of total daily calories. This helps support the high volume of glucose needed for that level of physical activity.

Each carb has 4 calories per gram. Endurance athletes should eat 8 to 10 grams of carbohydrate per kilogram (kg) of body weight per day. This will depend on the duration of their endurance event. For endurance training lasting 4 to 5 hours, endurance athletes should consume 10 grams per kilogram of body weight. 

For example, an endurance runner who weighs 70 kg and competes in an endurance event lasting 4 hours or more should consume a minimum of 700 grams of carbohydrate daily. In comparison, a power athlete would consume fewer carbs (around 4 to 5 grams per kilogram of body weight). A power athlete's focus would be more so to increase protein intake.

How Much Protein Should Endurance Athletes Eat?

Many people focus only on carbs for endurance exercise. However, protein intake for endurance athletes is equally important. The purpose of protein is to build and replenish lean muscle tissue. Protein also acts as a source of energy in times of caloric deficits.

There are two different types of protein:

• Animal-based protein

• Plant-based protein

Animal-based protein, as the name implies, is protein that comes from animals. It can come from the animal’s body, such as a cut of beef or fish filet. Or it may be a protein food they produce, like cow’s milk or an egg. This type of protein is considered a complete protein. It is complete because it contains all nine essential amino acids. Animal-based protein sources include:

• beef

• fish

• chicken

• eggs

• milk

Plant-based protein is protein that comes from plants. This type of protein can come from the plant’s leaves and roots, or from a fruit or nut produced by the plant. Plant-based protein is considered an incomplete protein. This isn't to say it is bad, it just doesn't have all essential amino acids. Plant-based protein sources include:

• almonds

• oats

• broccoli

• chia seeds

• quinoa

• hemp seeds

• peanut butter

Protein has 4 calories per gram. How much protein do you need to eat? Protein intake for a normal healthy adult is around 0.8 grams/kg/day. Endurance athletes should eat protein at 1.4 g/kg/day. Athletes taking part in longer endurance events need more protein than those running shorter distances. 

For example, endurance athletes weighing 70 kg would need to consume 98 grams of protein daily to support their endurance exercise. Athletes who take part in strength or power sports will consume up to 2.0 g/kg/day.

Endurance athletes on a plant-based diet will have an increased protein requirement. This is due to a plant-based diet consisting of incomplete proteins.

How Much Fat Should Endurance Athletes Eat?

Endurance athletes need healthy fats in their diet. Roughly 30% of one’s daily calories should come from fat when involved with endurance exercise. 

Dietary fat has six major roles in the body:

• Supply energy

• Help manufacture and balance hormones

• Form cell membranes

• Form the brain and nervous system

• Transport fat-soluble vitamins (A, D, E, and K)

• Supply two fatty acids the body can't manufacture (linoleic acid and linolenic acid)

There are many types of fat, some good and some not. The most significant types are triglycerides, fatty acids, phospholipids, and cholesterol. Of these, triglycerides are most commonly found in food. Fatty acids break down further into saturated, monounsaturated, and polyunsaturated fats. 

Endurance athletes need to minimize the amount of saturated fat consumed. Most fat calories should be in the form of monounsaturated fatty acids.

When adding fat to your diet to keep up with the demands of endurance training, focus your fat intake on healthy fats (1). This includes:

• Fatty fish - salmon, mackerel, or tuna

• Avocado

• Seeds - sunflower, sesame, and pumpkin seeds all have healthy fats

• Nuts - peanuts, walnuts, almonds, or cashews

• Olive oil

• Eggs

• Ground flaxseed

• Beans - kidney, navy, or soybeans

Important Micronutrients for Endurance Athletes

In addition to the three macros, endurance athletes also benefit from some specific micronutrients. Two to consider are vitamins C and D.

• Vitamin C is perhaps best known for boosting immunity. But it also serves other important purposes. One is that it is an antioxidant, protecting the cells against free radical damage. Another is that it supports wound healing. According to a 2017 study, vitamin C also helps athletes recover during the competitive season (2). Citrus fruits and potatoes are high in vitamin C. So are peppers, broccoli, strawberries, and kiwi.

• Vitamin D is important for bone health. Weak bones mean more fractures and breaks. A 2020 study also ties adequate vitamin D levels with improved athletic performance (3). Taking a cod liver oil supplement is one way to get more of this nutrient. Orange juice and dairy are also high in vitamin D.

Another Key Endurance Athlete Diet Consideration: Fluid Intake

We lose water throughout the day. It escapes our body through normal respiration, sweating, and urinary output. When we exercise, we lose more. 

Staying hydrated is more than about satisfying thirst. The top reasons for proper hydration, which are especially important for clients taking on endurance events, include:

• Promotes heat dissipation

• Improves performance

• Detoxification at the cellular level

• Regulation of blood pressure

• Promotes mental clarity

• Keeps joints and muscles lubricated

• Improves digestive process

Fluid Intake Guidelines for Endurance Athletes

Endurance athletes need to watch their hydration throughout the day, especially during workouts. As little as a 1-2% reduction in body weight due to water loss can result in decreased athletic performance.

Water intake guidelines are provided by the National Academies of Sciences, Engineering, and Medicine (4). Current guidelines are 2.7 liters (91 ounces) of water per day for women and 3.7 liters (125 ounces) daily for men. This includes water consumed both from beverages and food.

When your client is taking part in endurance activity, they need to up their intake. Here are some recommendations to follow:

• 2 hours before beginning endurance training: 20 ounces

• During endurance exercise: 10 ounces every 20 minutes

• After endurance exercise: 24 ounces for every pound of body weight lost

Replacing Electrolytes

In addition to water loss through sweating, we also lose electrolytes. When we sweat, we lose sodium, chloride potassium, magnesium, and calcium. These electrolytes serve important roles in supporting bodily systems. 

There are many electrolyte drinks on the market. These can help replace lost nutrients. Many exist in the form of a sports drink. The problem is that these drinks can also be high in sugar and calories. 

One of the best ways to replenish electrolytes after a long endurance training session is by eating whole foods. Here are a few options to consider:

• Sodium - chocolate milk, bagel with peanut butter, soup

• Chloride - olives, seaweed, celery

• Potassium - banana, sweet potato, dried fruits, avocado, kale, peas, beans

• Calcium - milk, yogurt

• Magnesium - whole grains, leafy vegetables, nuts, lentils, peanut butter

Nutrient Timing for Optimal Endurance Performance

Achieving peak performance requires having nutrients available when you need them. This can be accomplished by developing a nutrient intake plan. And this plan should provide nutrient timing guidelines.

Timing the intake of carbohydrate, protein, fat, and water is essential to endurance success. It involves laying out what to consume before, during, and after endurance training and endurance events.

Before endurance training:

• Consume 1 gram of carbohydrate per kilogram body weight 2 hours prior

• Consume 20 ounces of water 2 hours before the start of endurance training

• Carbohydrate loading should only occur leading up to an endurance event

During endurance training:

• Consume 10 ounces of fluid that have electrolytes and a 5% concentration of carbohydrate every 20 minutes

After endurance training:

• Consume 1.5 grams of carbohydrate per kg body weight within the first 30 minutes post-exercise

• Consume 15 to 25 grams of protein within the first 30 minutes post-exercise

• Consume 24 ounces of water for every pound of body weight lost

Nutrition for Endurance: Bringing it All Together

Nutrition for endurance involves a lot. But when endurance athletes pay attention to the recommendations and figure out what methods work best for them, the outcome is improved athletic performance. This can translate to higher awards come race day.

Whether you are an elite athlete, a weekend warrior, or a personal trainer designing programs for athletes, it is important to fuel the body properly. Proper nutrients at the right time allow the body to perform at its highest level.

Want to learn more about nutrition and its impact on sports performance? Check out the ISSA Nutritionist Certification and join a network of experts in sports nutrition.

References

1. Healthy Fat foods for your diet. WebMD. (2022, February 22). Retrieved April 19, 2023, from https://www.webmd.com/diet/ss/slideshow-healthy-fat-foods 

2. Heaton, L. E., Davis, J. K., Rawson, E. S., Nuccio, R. P., Witard, O. C., Stein, K. W., Baar, K., Carter, J. M., & Baker, L. B. (2017). Selected in-season nutritional strategies to enhance recovery for Team Sport Athletes: A practical overview. Sports Medicine, 47(11), 2201–2218. https://doi.org/10.1007/s40279-017-0759-2 

3. de la Puente Yagüe, M., Collado Yurrita, L., Ciudad Cabañas, M. J., & Cuadrado Cenzual, M. A. (2020). Role of vitamin D in athletes and their performance: Current concepts and new trends. Nutrients, 12(2), 579. https://doi.org/10.3390/nu12020579 

4. Institute of Medicine. 2005. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: The National Academies Press. https://doi.org/10.17226/10925.