01 May 6 Signs You Might Be Underfueling as a Runner

If there’s one thing runners need to do, it’s get enough fuel to perform their best. Here are 6 signs you might be underfueling, and what to do about it!

‘Fuel’ is a term you’ll often see used when reading about performance nutrition. But what exactly does it mean and why can “underfueling” be such a problem for runners?

But First, Fuel

Fuel describes the energy we get from the food we eat. It is usually referred to as ‘calories’ outside of performance nutrition circles, and is needed by our working muscles during activity.

“Underfueling” is a situation many runners find themselves in. Where they are just simply not taking in enough calories for the demands they’re putting on their bodies.

There are many reasons why this might occur. From concerns about body composition and weight, or perhaps a lack of understanding about the actual requirements of an athlete compared to the general population. Sometimes even having a lack of time to prepare and eat enough food.

Whatever the reason may be, underfueling and winding up with low energy availability is sure to be a detriment to an athlete’s performance.

It All Comes Down to Energy Availability

Energy availability is essentially the amount of calories you eat that are available to your body for physical activity, after taking into account your body’s needs for maintaining basic body functions.

For runners who spend hours and hours per week training, their energy availability needs are much higher than sedentary people. This is so they can fuel all that extra movement while also maintaining basic body functions.

In a low-EA environment, performance will definitely suffer, but our body’s basic needs may also go unmet. This can lead to a scenario we call ‘RED-S’, which stands for Relative Energy Deficiency in Sport. Basically, it’s when an athlete just isn’t taking in enough fuel.

Are you underfueling?

Here are some of the signs your calorie intake might just simply be too low…

Sign #1: You’re sick or injured constantly

What a lot of people don’t realize is that every process in your body requires fuel, not just physical movement. This includes things like digestion, breathing, circulation, and even your immune system!

If we don’t take in enough calories consistently, we’re likely to experience this immune system dysfunction which can leave us more susceptible to colds and infections.

If we have low energy availability this will also impact our body’s ability to recover from exercise. Since training demands are a source of ‘stress’ for the body, if we’re underfueling our recovery will be poor, increasing our risk of getting injured.

Sign #2: Your sleep quality sucks

Underfueling and low energy-availability can impact other parts of our lives, which in turn can have further impacts on our performance. Sleep for example is a key part of the recovery process from our athletic training.

Low energy availability can negatively impact sleep, which in turn will lead to poor recovery and further decrease our performance. It’s a vicious cycle that needs to be broken with simply getting enough calories in each day!

Sign #3: You feel hungry all the time, or have no appetite at all

This one probably seems a little obvious. If you’re hungry, you need to eat! I’m surprised at how often people feel they should be trying to “push past” or “ignore” their hunger signals, especially if fat loss is the goal.

For athletes though, when your body is asking for food, be sure to listen! On the flip side things can be a little bit tricky. Many Dietitians (myself included) will promote the use of our body’s internal hunger and fullness cues to guide when and how much we need to eat. And for many healthy people, it’s a great and reliable system.

Unfortunately, though for people who are chronically underfueled or going through periods of really intense training, appetite loss can be a side effect. Some people may also experience other digestive issues such as nausea, constipation or bloating with meals.

If you are feeling like your appetite has taken a hit and you’re skipping meals with ease, try setting a regular meal schedule with a timer to remind yourself that your body needs fuel to perform.

Sign #4: You’ve lost your period

For female athletes, the loss of our normal menstrual cycle is definitely cause for concern. Like all of our other body systems, the endocrine system (the body system dealing with hormones) can be negatively impacted by underfueling and low energy availability.

When we aren’t getting enough calories, our normal hormone function can be disrupted and one sign is losing your period.

This may not seem like a bad thing (I mean periods can be REALLY inconvenient!) but in reality these hormone imbalances can cause depletion of bone mineral density (leading to osteoporosis), or non-reversible infertility.

Sign #5: You can’t focus

We often think about our muscles requiring fuel to perform physically, but did you know your brain is actually the largest consumer of energy day to day? At rest, our brain requires 20% of the energy we get from food, and this must be from glucose.

If you’re feeling unfocused, have poor concentration, memory, or are moody and irritable, try giving your brain the energy IT needs to perform!

Sign #6: Your performance has taken a hit

One of the best ways to know that you’re eating enough is if your performance shows it. With proper training and adequate rest, you should be getting stronger, faster, and feeling good while you do it too.

If you’re feeling run down, slogging through your workouts, or need huge amounts of caffeine to push you through, it’s probably time to take a good look at your energy availability!

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The Bottom Line

Don’t let underfueling negatively impact your health and performance. Athletes, especially runners, need significantly more energy day to day than non-athletes. So being aware of how much fuel you really need to perform your best is key.

To learn more about what exactly you should be eating before and after a run, check out my blog post here!

Want to discover even more about how you can fuel better for stronger, faster running? Check out the Fuel for Runners online course!

Or, learn more about working with me here!

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