Endurance, Through a Functional Lens

Talking about fueling for endurance sports is about so much more than what to eat or drink during an activity. Well, that is if you care about health as well as performance anyway.

Although I am not a specific sports nutritionist or sports coach, I am an endurance athlete and a functional nutritionist that has worked with hundreds of athletes around optimizing how their unique body functions, including optimizing digestion, immune function, hormone health, energy challenges, sleep issues, mental health issues, injuries that won’t heal, and more. When we work from a grassroots level, focusing on the individual, it is amazing how people become more resilient and endurance ability improves as their body starts to function optimally.

Looking at Endurance through a functional lens helps us to see that above any protocol or plan, we bring our unique selves to the training formula and as it turns out that is the most important consideration.

It is crazy how varied the claims are about training and fueling and it’s no wonder so many people are left confused.

One side claiming keto is the most efficient. another side saying it’s dangerous and claiming we need fast carbs continuously. Intermittent fasting and fasted runs are either the best or the worst approach. Sports gels and gues are one man’s ticket to victory and another persons ticket to diarrhea. One woman claims high intensity interval workouts are most important while her best friend swears by long and slow workouts.

What if I told you they are all correct?

The truth is you need to find what’s right for you and your unique biology along with your unique goals. As Andrea Nakayama says, “nutrition is not just a handout”.

The key finding what is right for you is considering a systems biology perspective. When you do this you will be less likely to miss any key areas that might be keeping you back from performing your best AND you will support the proper body systems to ensure endurance activities don’t lead to long term health problems at the same time.

My sports fuel theory has always been ‘drink enough, eat enough, and refill after’. This seemingly over simplistic approach only makes sense after we look at Endurance functionally. (See my favorite trail foods below too though)

The basis of functional nutrition is considering what makes each person unique, considering all the body systems and how they interact, seeing each of our symptoms as something our body is trying to tell us, understanding that everything we do impacts how we function (including our mindset), looking for the root cause of symptoms instead of covering them up, and using food and lifestyle to optimize how a person functions now and in the future.

A big part of this is learning to track your unique body and learning to tune in and listen to what it is saying before it has to speak too loudly. See my favorite ways to do this below.

Signs you might have some work to do optimizing how you function-

Not having perfect poops every single day? Having any digestive problems? Or having problems sleeping? Any issues with your immune system? Experiencing energy ups and/or downs? Anxiety? Brain fog? Fatigue? Injuries not healing? Lacking strength? Not recovering well? These are all signs that need your attention if you want to perform your best or if you want to feel your best in 10, 20, 30+ years from now.

Have a listen/watch!

Listen to the discussion I had with my guru and teacher extraordinaire (I will be honest, she is my cerebral girl crush), Andrea Nakayama, about this topic. You can download the filled out matrix here as well to help you think into this systems based and empowering approach to endurance. It can be your trail map to using functional nutrition for health.


In my discussion with Andrea we talk about physiology and research around all the following functional topics and how they relate to Endurance

  • Mediators– what positively or negatively impacts endurance ability?
  • Digestion/Absorption (how endurance sports impact our gut and how our gut impacts our performance). We might have to do another entire talk on this one as it is so important.
  • The microbiome (so much great research around how our microbiome can specifically support our endurance efforts and vice versa. A healthy microbiome = health).
  • Immune function (long intense exercise impacts our immune function so how do we support our body so we stay resilient and strong. Plus, what is the difference between acute and chronic inflammation)
  • Energy production, how mitochondria function, fuel sources, and the aerobic vs anaerobic pathways
  • We dig into hormones and neurotransmitters including our stress hormone cortisol, thyroid hormones (so important for energy production and often overlooked and misunderstood), and sex hormones (because our monthly cycle is our 6th vital sign ladies!).
  • The value of high intensity training, strength training, mobility, and aerobic base training (which is the best? learn why we do them and you decide. I say include them all).
  • We run out of time but touch on mindfulness, community and staying positive (this is such a huge part of endurance so we may need to do another talk just about mental endurance and the power of our mind)
  • We talk about fueling and hydration tips also

Here is the completed functional matrix for Endurance Athletics- Loads of fun here to think about

Download the completed copy of the Matrix on Endurance here


Some of my favorite functional ways to track your unique body, to “look under the hood” so to speak, include-

  • Continuous blood glucose monitor or finger prick blood sugar monitor
  • An Organic Acids Test to look into fat/carb metabolism, nutrient levels, oxidative stress, mitochondria function, exposure to toxins and mold, gut dysbiosis, and neurotransmitters
  • A full functional thyroid lab to look in to the HPT axis
  • A saliva cortisol test to get a better look at you HPA axis
  • A gut zoomer to look into digestion, absorption, gut inflammation, the integrity of the gut wall, the diversity of microbes, or if there are any gut infections
  • Ketone meter to see if you are using fatty acids for energy
  • Nutrient panels to see if you are burning through any nutrients or needing to boost certain ones
  • Functional blood serum labs to get an overall picture of how your body systems are functioning
  • A urine hormone panel to look at sex hormones, sleep hormones, neurotransmitters, metabolites
  • Heart rate variability via a watch or Oura ring (my favorite way)
  • Basal body temperature to track your thyroid and ovulation/progesteron
  • Heart rate chest strap to measure your heart rate at different intensities
  • Genetics, when indicated

And footnote- don’t be surprised if your doctor isn’t interested in this testing as to them you seem to be in perfect health. The thing is, perfect health is not the only other option than diseased/medicated. The truth is there is a huge spectrum in the middle and we are talking about optimizing that. Find someone who will help you.

Did I mention that I love data? Become your own scientist!

There is a lot we can learn from just tracking our body with a pen and paper (or fancy app) too



A few of my favorite foods to fuel long endurance adventures include

  • Boiled potatoes and salt (always)
  • White rice and bacon squares (this is what I am eating in this picture and as you can see it brings me a lot of joy on the trail:) Ymmm)
  • Salted nuts and raisins
  • Nut butter
  • Avocados and bean burritos
  • Homemade cookies, bars, gummies (you can download a few of my favorite recipes below)
  • Dried dates and mango sticks
  • Honey sticks and other bee products like royal jelly and propolis
  • Puréed sweet potatoes and applesauce
  • Olives and soft stick beef jerky (seriously)
  • ginger chews
  • Packaged foods and hydration that I like- Scratch Labs electrolytes, LMNT electrolytes, Trail Butter, Spring gels, Rx bars, Snickers, Honey Stinger gluten free waffles, Amy’s gluten free bean burrito (this one warms up great in the pack all day;)), Kion Aminos
  • Pre endurance adventure foods– about 2 hours before I head out I love to eat sourdough toast with almond butter and bananas or a bowl of hot millet cereal with maple syrup and walnuts. 30 minutes before heading out I drink a scoop of amino acids in water (I try to do it again every 90 minutes or so).
  • Post endurance adventure foods- I always eat some carbs and protein within 30 minutes of finishing up on the trail. That often includes a mango and protein smoothie or my superfood recovery smoothie.

CHECK OUT SOME OF MY FAVORITE RECIPES FOR TRAIL FOODS AND PRE/POST ADVENTURES HERE

What are some of your favorite trail foods? I would love to hear. Share below or on instagram @mountainrebalance


A few of my favorite books and tools for training functionally include-

Above all else, Functional Nutrition teaches us to be curious about our body and what is going on before it has to talk too loudly. Enjoy the trail and as Thick Nhat Hahn says “Kiss the earth with every step”

Janel Ferrin Anderson DNM FNLP NC

Janel is obsessed with helping people understand their unique body and figure out how their food and lifestyle choices impact their health. Janel helps people explore the root cause of signs and symptoms and how to tune into what their body is saying. Janel is a board certified nutritionist, a certified functional nutrition practitioner, has her doctorate in natural medicine, and is a certified family herbalist. She is a passionate mountain athlete, food junkie, and science nerd. Janel works one on one with clients and teaches many groups. Learn more about Janel here

Badass For The Long haul (currently being reorganized)


Studies and Research from my talk-

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