Nutrition for Endurance Training

Nutrition for Endurance Training

Are you an athlete? Then you need to eat, sleep, and train like one.

FLEXIBLE DIETING is: “A diet that doesn’t impose any restrictions on food sources or choices, and employs a monitoring system that looks at quantitative data – i.e. calories and macronutrients. The degree and strictness of the monitoring can be altered and changed depending on the individual’s goals, preferences and lifestyle. Flexible dieting doesn’t ban or restrict any foods, and it doesn’t even judge foods or food groups as good or bad. Each individual item can only be viewed in the context of a diet as a whole.”

How do you get started?

  1. The most important step is establishing energy balance. Find what your body needs in terms of calories to perform well. 
  2. Track your macronutrient intake, which will tell you not only your daily calories, but whether you’re optimizing your fuel sources. Appendix B at the end of this document will help you determine your starting macronutrient goals. 
  3. Establish micronutrient balance by eating diverse foods. 
  4. Further refine your performance and recovery through proper nutrient timing and supplementation


Tracking Food Intake

If you track your workouts, you most certainly should track your energy intake. Keeping tabs on your macronutrients (carbs, fats, and protein) will not only help you get the appropriate amount of calories, but ensure that you are fueling body according to your performance needs. The easiest way to get started is to keep a food journal (such as MyFitnessPal) and track your macronutrients and fiber for a week. 

When starting off, you will first want to assess your average caloric intake. Based on your trends, you will set goals for macronutrients and overall calories.  For example, if your seven day average is 2,300 kcal a day and you are dissatisfied with your performance, you may try to raise those calories a little at a time. People normally see the most inconsistency with training when they undercut calories. 

See Appendix A for macronutrient splits. Look at your averages and decide on a goal. 

Marathon Training

Intra-Training Nutrition


Endurance athletes are faced with a dilemma. Common knowledge tells us to consume simple sugars during exercise and that overconsuming simple sugars is bad for you. So what do we do? For endurance athletes, the primary problem with simple sugars is actually that they must be mixed in a weak, 68% solution in order to match body fluid parameters and to be digested efficiently. A mix of this concentration only provides 100 kcal per hour at the most and is thus inadequate for energy production maintenance for most athletes. 

Instead, I recommend complex carbohydrates (polysaccharides) for endurance athletes. As a more efficient fuel source, complex carbohydrates allow the digestive system to rapidly process a greater amount of calories and provide steady energy (Carbs are your friend, athletes!). You can also combine simple and complex carbohydrates. You will just want to make sure that in doing so you can fulfill your caloric requirements without risking over hydration or other stomach-related maladies.



When exercise extends beyond two hours, your body begins to utilize some protein for its energy requirements. If you do not incorporate protein intra-training at this point, your body will resort to consuming its own muscle. I usually recommend protein supplementation in the latter portion of the race to avoid excess muscle breakdown. This might also help with help with reducing delayed onset muscle soreness and decrease overall recovery time.

For clients who compete in races longer than 1.5-2.5 hours, I recommend that they do not get too many of their calories from solid food. Rather, liquids and gels provide the best nutrition density and they are easily digested. I do not recommend using anything in a race that you have not tested in training. 

For clients who compete in something more interval-based such as CrossFit, I recommend solid food (especially with some fiber) to control hunger. Solid food will also help prevent you from burning through fuel too quickly with metabolic training and heavy compound movements.



Too many athletes eat under the premise that they must restore every calorie they burn to avoid bonking. An endurance athlete exercising beyond 1 or 2 hours, though, is a deficit-spending entity. Your body cannot replenish calories as quickly as it expends them – same with fluids and electrolytes. Instead of trying to replace all those calories, you can rely on body fat and glycogen stores, which can easily fill the gap between energy output and fuel intake. 

Because it’s overkill to attempt calorie-for-calorie replenishment, I recommend that athletes try to maintain a consistent calorie intake and a balanced macronutrient structure over an extended period of time. In general, 120-150 kcal per hour is absolutely sufficient for an endurance athlete of about 160-165lbs (72.5-75kg). Lighter athletes (120-125lbs or 54.5-57kg) will need fewer, and those above 190lbs (86kg) may need more. All athletes will differ, which is why tracking food, water, and sleep is so critical for optimizing performance.


Pre- and Post-Training Nutrition 

You will want to experiment with different foods under different conditions to determine what works best for you. Most people see great results eating the majority of their carbohydrates around training sessions, particularly the meal prior to training, a snack about an hour before training, and directly after training. Following endurance workouts, you will want to get glucose and protein into your system as quickly as possible—ideally, within 30-60 minutes. A 3:1 carb:protein ratio is reasonable for endurance athletes, especially if lean muscle-mass recovery is the objective. Depending on your macronutrient needs, this will be 30-90g of complex carbohydrates and 10-30g of protein. 

There are many convenient products out there that can help you fit in post-workout nutrition even if you’re on the run. A glutamine-fortified whey protein isolate can also help with antioxidant replenishment, and some protein powders also come with carbohydrates. In some cases, a 4:1 carb: protein ration may be beneficial—particularly for those who are already lean and are not predisposed to carb-induced fat gain. 

If you train in the morning, you will want to get to the point where you start to load up on food (lightly) the night before. You will still want a calorie-dense snack about an hour or ninety minutes before training and then follow with protein and carbs post-training. 

Nutrition for Endurance Training


Unfortunately, endurance athletes often have the mindset that “if a little is good, a lot is better.” Optimizing nutritional support, however, requires consuming the right amount of the right nutrients at the right time. Both overloading and under supplying your body will compromise athletic performance – among other detrimental results. This principle of avoiding both “too much” and “too little” applies especially to hydration, and there are serious consequences for both. In fact, over hydration can even risk life-threatening water intoxication!  

One of the most respected researchers on hydration, Tim Noakes, observed thousands of endurance athletes for hydration practices and side effects. He found that the front runners typically tend to dehydrate, while those in the middle of the pack and the back of the pack tend to over-hydrate. Both lead to hyponatremia (low blood sodium) through different processes. 

If both too much and too little fluid will get you in trouble, how much should you drink? Between 500 to 750 mL an hour (about 17 to 25 fluid ounces) will fill most athletes’ hydration requirements in most circumstances.



Micronutrient deficiencies can cause major problems in athletes. A particular concern among endurance athletes is inconsistent electrolyte replenishment. You do not want to wait until you are dehydrated to drink fluids or you will bonk before you put calories back into your body. You wouldn’t wait until your car engine seizes to refill the oil; the same is true for nutrition. Electrolytes are the body’s motor oil. You don’t want to start cramping before restoring these important minerals. This does not mean, however, that athletes should just indiscriminately down sodium, potassium, etc. As with hydration, balance is key. 

Ideally, you would want your potassium levels to be equal to or greater than sodium—a 1:1 ratio or even 2:1 if possible. More often, though, most diets tend to be low in potassium and high in sodium. In athletes, this can cause muscle cramping and fatigue. If you have low potassium (hypokalemia), high blood pressure, or if you are taking diuretics, you may need more potassium. Your healthcare provider can tell you more specifically how much potassium you need per day.

The following foods can all help increase your potassium intake, and they all contain more than 200mg of potassium per serving:

    • 1 medium banana (425mg)
    • ½ of a papaya (390mg)
    • ½ cup of prune juice (370mg)
    • ¼ cup of raisins (270mg)
    • 1 medium mango (325mg) or kiwi (240mg)
    • 1 small orange (240mg) or ½ cup of orange juice (235mg)
    • ½ cup of cubed cantaloupe (215mg) or diced honeydew melon (200mg)
    • 1 medium pear (200mg)

You can also supplement with potassium-rich drinks such as coconut water!  


Game Time

If you have a coach, you’ll want to maintain consistent communication the week of your event, or even 30 days out from the event. As you get close to the competition, you’ll want to stick with familiar foods. Right before the event, make sure you consume something familiar that you know your digestive track can handle.  

A common mistake is over consuming food the night before a race or competition in hopes of “carb-loading.” It would be nice if we could maximize muscle glycogen stores the night before, but unfortunately, human physiology doesn’t really work that way. Increasing muscle glycogen stores takes many weeks of consistent training and tracking as well as post-workout replenishment. If you overconsume the night before, your body will pull the excess calories into fat storage. 

Just eat the same balanced meals you have been consuming throughout training. Something like 200-400 kcal before training sessions is beneficial—carbohydrates and perhaps a small amount of protein is good. Keep fiber low or nonexistent. If you have a longer event, you may choose to add a small amount of fat. A Cliff Bar, for example, would work well here. If you need something 5-10 minutes prior to the start of a race, 100 kcal of easily digested complex carbohydrates would be appropriate. Make sure you log what you eat and how you feel throughout training so that you have a plan for Game Day. 

It should go without saying that alcohol the night before (or the morning of) a race would damage your performance.


Revising Your Game Plan

If you perform less well than expected, you would be well-served to adjust your nutrition plan. Many athletes will respond by ramping up their training—going harder and longer. Oftentimes, this will lead to even worse recovery and performance and even poor immune function and hormonal imbalance. A better tactic is to recuperate after the competition, assess the situation, and modify training and nutrition after a rest period. 

One of the more damaging mistakes endurance athletes make is sticking with their game plan even when it’s not working. If you feel like you need a little bit more, you probably need a little bit more. Note this and make adjustments in your macronutrient base. You will never know what works best for you if you don’t experiment a bit.



Adherence really is the most important factor of any diet or nutrition program. No matter how good the diet is, if you cannot follow it consistently and long-term, it will not be sustainable. Even if you manage to get the desired results, if you can’t maintain those eating habits for the rest of your life, you also cannot keep those results. That’s why it’s important to find an approach that you find enjoyable and one that you can keep indefinitely. Essentially, you want to make your diet a lifestyle, not a temporary period of unnecessary suffering and restrictions.  As athletes, we want to stay healthy and be able to sustain this career that we love. We want to be able to train for the rest of our lives. Optimizing your nutrition is a key component in achieving that longevity.

Source: Garrett Hayden



If you subject your body to the rigors of extreme training, then in addition to monitoring your nutrition, you will also want to get adequate sleep for recovery. On days that you do not sleep well, you may notice that you move slower and feel worse. Training with inadequate sleep can also cause injury as well as hormonal imbalances and further oxidative stress.


Some women will experience substantial fluctuations in strength depending on their cycles. 48-72 hours before menstruation begins, many women will feel more fatigued. This is a good time for lower volume and lower intensity workouts. LIIS instead of HIIT might benefit the athlete. Being cautious around this time will reduce swelling and fatigue. This patience will also pay off because for two weeks following menstruation, most women will experience an increase in strength. That means that in the week following menstruation, you should go hard!




How do I begin to track macros for endurance and aesthetic goals? 

Because flexible dieting is flexible, it offers many options for macronutrient ratios. Appendix A offers some suggestions. You can start here after 7 days of consistent tracking. 


Appendix A

  1. The BALANCED Macro Plan: 35-40% P / 40-45% C / 20-25% F 

This is great for people who are eating a fairly balanced diet and average 20-25% kcals from fat. This plan should allow you to push calories up by adding calories to all 3 macros as needed. 

  1. Equal Split: 33% P / 33% C / 33% F

This is an easy way to maintain weight. You can go hard for 45min – 1 hour or for shorter bursts of interval training. In some cases, this fat % may be too high for ideal aesthetics. 

  1. High Fat: 20-25% P / 15-20% C / 55-70% F

This breakdown is often used for managing cancer and epilepsy. It can also fall into the category of “keto dieting.” It is not recommended for performance at all. If you need to eat high fat (or do so out of preference), you would need to be certain to hit your fiber needs (5-10g per meal, depending on the individual). Make sure your carbs come from high-quality, complex sources such as beans, veggies, fruit, and fiber-filled grains. 

  1. High Carb : 15-25% P / 55-70% C / 15-25% F

This is another option for endurance athletes, bodybuilders, and the sport performance crowd. You’ll want to achieve this ratio over time by starting at 55% carbs, increasing slowly while decreasing protein and fats, adjusting weekly or bi-weekly. 

  1. High Protein: 60-70% P / 15-20% C / 20-25% F 

This option is for people looking to lose weight quickly and minimize hunger. Protein should not exceed 1.2g – 1.4g per pound of body weight. Under normal circumstances, athletes do not need more than .7-1.2g per lb of body weight. Recent studies (2015-16) by Alan Aragon, Brad Schoenfeld, and Dr. Lehman show that the above numbers are sufficient for most populations. 


Appendix B

Step 1 Overall Calories

_____lbs body weight x 10-12 depending on activity level (10 low / 11 moderate /12 intense) = _____ kcals for overall daily intake


Step 2 Protein 

_____lbs body weight x .7g-1 g per lb body weight = _____ grams of protein x 4 = _____ kcals from protein


Step 3 Fat 

_____lbs body weight x .25g-.4g = _____ grams of fat x 9 = _____ kcals from fat 


Step 4 Carbohydrates 

_____ overall calories  – _____ kcals from protein – _____ kcals from fat = _____ kcals from carbohydrates

_____ kcals from carbohydrates/4 = _____ grams of carbs 

Ready, set and GO! 


Have more questions about Macro’s and working with KMF for your fitness needs? Fill out this health questionnaire and we will schedule a free 15 minute consultation to get started. 

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