Fueling Performance – 5 Nutrition Rules Every Endurance Athlete Should Know

Updated: Jun 2

There’s no doubt: you, the endurance athlete, have unique needs when it comes to nutrition. To find your competitive edge and fuel the physical demands of your sport, you require many additional nutrients. The influence of proper nutrition shouldn’t be underestimated, and should be done with the aim to optimize performance during sports, while reducing recovery times afterwards. Let’s get back to the basics with 5 nutrition rules that will have you ready to go on race day.

#1. Day to Day Nutrition Matters the Most

What you eat on race day is very important, but the biggest problem facing endurance athletes is how you eat on the non-race days. Eating a balanced, clean diet every day, while maintaining nutrient density will provide a good supply of high-quality energy to working muscles.

I like to remind my clients, ADDITIVES ARE SUBTRACTIVE. If you eat junk, your body will have to steal from its own nutrient stores to get rid of the toxins you just put in your body…. key nutrients that you need to fuel all the biochemical processes to make you go that one extra mile. Eating a balanced, clean diet means plenty of fruits and vegetables, high-quality proteins, adequate fiber, and essential fats. “Everything in moderation” for an athlete really needs to mean “rarely”. Go ask any professional race car driver how many times a month they put regular unleaded gasoline in their prized winning machine. My guess is the answer is something like “never”.

#2. Know Your Calorie Requirements

This is probably good advice for most anyone, but athletes in particular need to know how much fuel they require to run. A quick google search will find you a Basal Metabolic Rate (BMR) calculator. BMR will tell you how many calories your body burns doing its basic functions, like sleeping, digesting, and breathing. From there, you can multiply your BMR by the following numbers depending on how active you are. This should give you a ball park of how many calories you should be eating.

Moderate Exercise 3-5 days a week: BMR x 1.55

Hard Exercise/Sports 6-7 days a week: BMR x 1.725

Extra Active with more than one workout per day: BMR x 1.9

Alternatively, if you have a watch or system that calculates your calorie burn during workouts, simply add that to your BMR to know your break-even for the day. While I am not a huge proponent of counting calories on a daily basis, recording what you eat for 3-5 days in an app like My Fitness Pal will give you a good handle on what you are actually consuming and if it’s enough to power your energy requirements.

#3 Balance Macros According to Training Load

Training load should dictate your macros. And back to my previous recommendation, 3-5 days of painfully and diligently recording everything you consume in My Fitness Pal will tell you exactly the percentage of macros you currently eat. From there, you can better adjust your diet to reflect how many carbs, fats and proteins you need to be eating.


Carbohydrates are essential to endurance sports. The keto-favoring world will not like it when I tell you this, but keto and high-intensity endurance sports will not be good friends. The higher the energy requirement, the higher the carbohydrate intake should be. The body just cannot sustain without it. The muscles store carbohydrates as glycogen as their primary energy source, and without it, there are negative consequences to adequate endurance potential and recovery times.

I am a big proponent of the Modified Paleo Diet. More on that another day. Basically, what it boils down to is, on the days you are training heavy, you increase the carbohydrate load by adding in root vegetable, starches, and a higher percentage of fruits and vegetables. Potatoes, beets, yams, and yucca root become part of your day. Refined carbohydrates are still avoided. Gone are the days of big bowls of pasta. Carbohydrates should encompass at least half your plate and will act as your main source of energy, vitamins and antioxidants.

Besides being the muscles preferred energy source, carbohydrates provide several other key nutrients that fats and proteins cannot - vitamins, minerals and antioxidants. And this is where I break in and say, “not all carbohydrates are created equal”. Eat the color of the rainbow and you will find these key nutrients. Vitamins and minerals act as co-factors to fuel all the biochemical processes in your body. So, let’s take that bagel you had for breakfast as an example. Yes, it had the amount of carbs you needed. But those carbs will not be getting into the cells and turned into energy without B-vitamins to fuel the process. Does the bagel have the b-vitamins you need? Not really, not in forms your body can use. The leafy greens on the other hand do. The kicker here is that the higher your training load, the higher your energy requirements, and then higher your need for B-vitamins is to shuttle those carbohydrates into the cells for energy making. If you’re not getting in adequate B-vitamins through diet or supplementation, or you are burning through them during your high intensity workouts, eventually your power output is going to suffer.

Additionally, all that exercise you are doing is generating a lot of oxidative stress within the body which needs to be counteracted with antioxidants. These are found in anything with color – bright fruits and vegetables. Processed grains drive inflammation further adding to the oxidative stress count on the body.


On days where you are recovering or training lightly, increase fat percentage relative to carbohydrate. Eating more fats on your “off” days will allow the body to become more efficient at burning them, and will help delay the use of your glycogen stores. Fat has an essential role in providing energy during periods of rest and low-intensity activity. It also has a role in hormone production and immune function. The right fats are very important so emphasis should be on choosing fats from coconut, avocado, and olive oils, wild caught fish, as well as consuming nuts, seeds and nut butters.


Lastly, discover your protein need. Protein helps build and repair tissues and is required for recovery. I think of protein as legos. You eat a fully assembled lego set, and your body breaks it down into the individual pieces so it can use those to make or repair something else. Protein also helps carbohydrates be more efficiently stored in the muscles as glycogen. When determining macro ratios, its easiest to start with determining your protein need as that should stay pretty constant. Then fill in percentages of carbohydrates and fats according to training load.


< 5 hours of training per week = .6 grams OR 2.4 calories per pound of body weight

5-10 hours of training per week = .7 grams OR 2.8 calories per pound of body weight

10-15 hours of training per week = .8 grams OR 3.2 calories per pound of body weight

16-20 hours of training per week = .9 grams OR 3.6 calories per pound of body weight

> 20 hours of training per week = 1.0 grams OR 4 calories per pound of body weight

#4 Don’t Guess at Your Micros

By micros I mean the vitamins, minerals and antioxidants. It seems every athlete chasing the next best supplement without real knowledge about how it works in the body, what interactions it has with other vitamins (some vitamins deplete others), and if your body truly needs it. Just as you would measure your functional threshold power, or your VO2 max, it’s also important to measure what’s going on inside the body to know what you really need. It’s very likely your combination of diet and exercise load will be causing depletions you are unaware of, which if left unchecked could drive you into a state of overtraining, fatigue or some type of health problem.

Micronutrient testing solves just this problem. Standard blood serum tests that your doc might order like B12, magnesium or folate, don’t really tell us much because a vitamin in the blood serum is virtually useless to the body. Not until it enters the cells, does it drive biochemical processes in the body. Intracellular testing is also not affected by what you ate that day, or by how hard you worked out. And the beauty of it is, that once you know your deficiencies, you can work with your nutritionist to formulate the perfect supplement program tailored to exactly what your cells need. Feed your cells what they need and optimal health and performance will emerge.

#5 Have a Plan for Race Day Fueling

Race day fueling, and how you fuel the week leading up to a race is very important. This crucial element should be a priority to figure out, long before you find your way to the start line. In our next blog post, I’ll tackle just that: how to fuel for various races of different lengths. Stay tuned.

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