One Dirty Magazine

Ask The RDN: Top Nutrition Mistakes Runners Make

These are the most common mistake our RDN sees runners make in their nutrition and training.

Kylee Van Horn, RDN September 23rd, 2020

Ask The RDN: Top Nutrition Mistakes Runners Make

I get it.  You heard about the latest nutrition trend and want to incorporate it right away into your daily routine to try and improve your running performance. For many runners, failing to optimize performance comes down to the fact that they don’t have their nutrition basics dialed in.  When I work one-on-one with runners to improve their nutrition for health and performance, it’s not that someone is deficient in a weird vitamin or nutrient, or that they need to eat a certain diet for their blood type (don’t do that). More often than not, it’s that they haven’t quite nailed their nutrition basics.

While it’s not exactly rocket science, dialing in the following nutrition principles can help you make the biggest health and performance gains.  Let’s take a look at the most common mistake I see runners make when it comes to nutrition.

#1) Not Eating Enough:  This is the most common mistake runners make.  No matter what your goals are, if you aren’t eating enough, it can have a cumulative effect and lead to imbalances in hormones, nutrient deficiencies that can lead to a higher risk of injury and illness, and long term ability to adapt to your training. Research shows that within-day energy deficits have detrimental effects on health and performance, particularly for female athletes.   Some signs that you might not be eating enough are poor sleep patterns, inability to recover from training, frequent illness or injury, frequent bouts of hunger, and a loss of period (amenorrhea) for female runners. 

Easy Solution: Making sure you have a loose eating pattern set up for yourself, as well as a full pantry and go-to snacks to make it easier to eat enough.  Avoid restricting macros or any food-groups, and have a plan to fuel pre-run.  If you are having trouble dialing this in, reach out to a sports dietitian for help. 

#2) Not Focusing Enough on Pre- or Post Workout Nutrition:  If you are concerned about performance, honing in on your pre or post-run nutrition is a critical step.  Not eating enough or timing things poorly beforehand can lead to higher incidences of GI distress, increased risk of injury and a higher risk of bonking.  Post-run, your nutrition can influence whether you come back strong the next day and can increase or decrease your injury risk.  Making sure you’re eating enough of certain nutrients like protein will give your body the best shot at recovering and being ready to roll the next day. 

Easy Solution:  Get in the habit of eating something before your runs that contains mostly simple carbohydrates and a little bit of protein.  Some ideas include a banana with peanut butter, toast with sunflower seed butter, or quick cook oats with almond butter.  After running, drinking your calories can be a good option, especially if you are not hungry or in a rush.  Either whip up a banana smoothie with some Greek yogurt or simply add protein powder to some sweetened almond milk.  

#3) Not Practicing an Inter-Run Fueling Plan: Winging it during long runs and adventures might seem like a good idea….until it’s not.  There are three things that affect your body’s ability to run well for long periods of time: the volume of fluids consumed per hour, the amount of electrolytes consumed per hour, and amount of calories/types of calories consumed per hour.  These three pillars of inter-run nutrition work best when dialed in to work together.  Get in a hole in one of them, you risk stomach distress, bonking, and having to slow down.  

Easy Solution: Start with choosing a fluid per hour goal, real food blend/gel option, and 2-3 real food options for fueling.  Put together an organized plan for yourself aiming for the general recommendations of 200-300 calories per hour, 250-500 mg of sodium per hour, and 16-20 oz of fluids per hour.  Put into practice during your long runs and adventures. 

#4) Not Hydrating Well: Being even two to four percent dehydrated can lead to a decrease in running performance.  Water is critical to delivering oxygen to the muscles, assisting with nutrient absorption, and regulating body temperature through sweat.  Signs and symptoms of dehydration include: dizziness, dry lips and skin, increased body temperature, decreased pace and fatigue and darkened urine.  

Easy Solution: Start with calculating a general estimation of your fluid needs per day.  ½ your body weight in ounces plus 16-20 oz for every hour of exercise you are doing is a good place to start.  Once you dial in a goal, aim to increase your current intake by 8-16 oz per day for a week or two, and gradually increase until you reach your goal. 


Do you have a question for our RDN? Send your trail-running-nutrition quandaries to

Kylee Van Horn is a licensed Sports Registered Dietitian and competitive trail runner.

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19 days ago

Great article! You kept it real simple for us that are easily distracted and I picked up on a few real easy tips. As a 75 year old trail runner, I need all the help I can get. I know this will make a difference, and it’s so simple that even I will do it. Thank you!

17 days ago

Thanks for the great basics article. The only thing I’d pick at is the electrolytes part. I used to cramp up in hard races and take electrolytes. Then I ready Waterlogged, stopped taking them, and the propensity to cramp was just the same during hard races, but I solved it by understanding the underlying mechanism better. The key there (since really, if I cramp at hour 3 in a race, but never in a 7-9 hour training run, how can it be electrolytes and not muscle overexertion) was simply combating cramps with a heart rate monitor. In a hard race, if I feel cramps coming on, I can ensure I NEVER cramp by keeping my heart rate below a certain level. Go 4+ beats above that, and BAM, a cramp.
Yeah, yeah, I know everyone’s an individual, people sweat different, etc., but by understanding (and then addressing) my cramps as a function of muscle overexertion, I went from a guy who would take electrolytes from the starting gun and religiously cramp at 3-4 hours every race, to running another 12x 100 milers, including super hot races (32 hours in Greece in Sept) with no cramping and no electrolytes. You can call that a sample size of one, but we are all still humans, and are not THAT different.


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