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Low Daily Energy: How Undereating Affects Motivation & Training

Critical Concepts Series: Energy In, Energy Out – Part One

Low daily energy is affecting more than just your training as a female athlete. Here’s a story to illustrate:

“Okay, so this week has been the worst in a long time!” 

This was the opening line from an athlete-client I’ve been working with, Michelle*. She went on to explain how her motivation from the previous week had fallen to pieces.

She had defaulted to fast-food meals five days in a row. Plus, she skipped the gym entirely.

This is part one in a series of understanding the critical concepts of energy and energy balance and why they are so important for athletic women.

  1. Part one – this article – focuses on the link between stress, overwhelm and lack of energy / motivation.
  2. Part two will look at why “energy in, energy out” is more nuanced than “calories in, calories out.”
  3. Part three will focus on the factors of metabolism, total daily energy expenditure, including non-exercise activity thermogenesis and purposeful physical activity.
  4. And in part four, you’ll learn about how to boost metabolism over 40 as an athletic woman.
banana on a container of overnight oats for better daily energy next to shaker bottle and red weightlifting shoes

“Mentally I’ve been struggling,” she said. “Work’s been crazy and all I wanted to do was eat sugar all day. I bought all the food for meal prep over the weekend and didn’t make any of it. I was just lazy.”  

And there it was. The self-defeating character flaw. “I was just lazy.” Except she wasn’t.   

Like so many female athletes I work with, Michelle wasn’t lazy at all. In fact, the opposite was true. 

Overwhelm Leads to Undereating

Michelle’s problem wasn’t laziness; it was overwhelm.

This overwhelm caused her to undereat across the day – often just a coffee for breakfast and skipping lunch to fit in meetings – as she struggled to keep up with a very demanding work schedule.

Then, at the end of the day, fatigued and frazzled, there was no energy left to prepare, cook, and eat a good meal, even with everything that she needed sitting in the cupboard. And she was too drained to get her lifting done.

It was a similar story with Tracey*. She came to me seeking help for her low energy, low mood, and low motivation.

She knew training – lifting and biking – made her feel good, especially mentally. But the motivation to start anything had escaped her. As she felt her fitness fall away, her motivation dropped even further.

Sensing that there must be something wrong with her, thinking that she must be broken in some way, she went to her doctor and left with a prescription for antidepressants.   

Is Your Energy Depleted?

Tracey, trying to reduce her body fat and drop body weight, started intermittent fasting, up to 16 hours at a time, daily. She combined this with a low protein diet – low animal source foods, in particular.

white woman with brown hair sitting on gym floor holding overnight oats and a spoon

She lifted weights and did CrossFit in the morning. At 1 pm she ate her first meal. But by that point, she was drained and sleepy.

(Side note: This kind of training and fueling pattern especially sets athletes up for within-day energy deficiency.)

Tracey would often wonder what was wrong with her. But she wasn’t broken.

She was depleted of energy, and, given her food habits, probably depleted in many nutrients like amino acids, vitamins, and minerals.

Within two to three weeks of eating more – increasing her protein energy intake via nutrient-dense animal source foods in particular – she was feeling far more energetic, getting to the gym, and riding her bike again. 

Over the next few months, Tracey started adding more muscle mass

The pattern is a common one, probably the most typical that I see currently with my private coaching clients and students

Before you start beating yourself up for being lazy or hopping on a new training plan to try to fix things, you first need to repair your energy.

Why Do Athletes Underfuel?

Athletes may undereat for one reason or another.

1) Intentional dietary restriction

Sometimes, it’s intentional dietary restriction, especially if there’s pressure to be leaner or lighter(1).

This could take the form of restricting a specific macronutrient such as carbohydrates, fats, or protein. It could also be from intentional calorie reduction in attempts to lose weight or body fat.

Fasting, low carb, and low protein are common amongst athletes.

2) Unintentionally eating too little compared to activity level

Other times, it’s undereating among athletes is unintentional.

You might try to “eat healthy” but you don’t realize you’ve made too many low energy food swaps.

Getting adequate daily energy could be challenging if you’re traveling. Younger athletes might not have as much control over food purchasing and prep.

And still other times, you just might not realize how much energy it takes to fuel your training and cover your basic bodily functions.

Or perhaps the hectic nature of life and training take over, and other things get prioritized over fueling yourself. Coffee is seen as a meal. A bar on the run will get you through.

If you can make it to dinnertime, you’re golden. But sometimes, by that point, you’re so exhausted from making decisions all day that the only thing you can think of is ordering takeout again.

3) An increase in energy output without increasing daily energy intake.

Maybe you’ve increased your training volume or intensity but not compensated by eating more.

You could be eating the same amount as before but with more energy going out, now you’re at a deficit.

close up of hands unscrewing the lid from a jar of overnight oats and berries for more daily energy

You don’t intend for it to be this way, of course. You have good intentions, and high expectations.

When you actions don’t meet our expectations – which is often when we are operating in such a low energy state – you despair.  You internalize the low energy you’re experiencing as being “unmotivated,” “lazy”, procrastinating, and “just making excuses”.

The emotional regulation required to pull you out of such a tailspin itself requires significant energy. 

Low Energy Affects Daily Activity Levels

All elements of your daily living, training, health, and well-being are interconnected and all require energy. Indeed, energy is the currency of deep health.

When you get dragged down into the busy-ness of life you can lose sight of how important your energy is and what it takes to recharge.

Yes, there’s the physical energy required for you to engage with any form of intentional physical activity, exercise or training. But you also need energy for all of the non-structured physical activity, too.   

white woman with brown hair squats with an empty barbell on her back

Ever found yourself taking the elevator because you were too “lazy” to take the stairs? Or driving around the same parking lot over and over again to find the closest parking space because you “can’t be bothered” to walk too far?

When athletes tell me they’re just not motivated to do anything, that’s a big red flag to check for energy intake.

The stories you tell yourself about your behavior can give you insight into your energy balance or lack thereof.

What Else Your Body Needs Energy For

Physical energy is also required for other parts of you body, not just for your muscles to move you around during training or competition.

Here are just a few to consider:

1) Your gut and its ability to digest and absorb nutrients requires energy.

Deprive your digestive system of energy to do its job properly and you’re going to experience problems.

Everything from the ability to break down and digest the food you eat, to the capacity to absorb the nutrients, to the muscular components of your digestive tract (which can become “slow” and “lazy” when we are in a chronic low energy state), require sufficient energy to function optimally. 

2) You need enough total daily energy for your brain.

A lot of energy.

Despite its size, it uses a disproportionately large amount of the fuel you take in. Deprive your brain of sufficient fuel and you can experience changes in cognition and behavior. And yes, women athletes need carbs. No, coffee and fasting are not fuel for your brain.

Decision fatigue and brain fog are common, as can be increased anxiety. As already stated, your ability to regulate your emotions requires that your brain is well-fed (and well-rested). 

white woman with brown hair squats down with her hands on a barbell

3) Bone health requires enough energy.

You might think of low bone density or osteoporosis as problems that only strike women over 50 due to the sharp decline in estrogen post-menopause.

But though low energy availability impacts both male and female athletes, women in particular, are at risk for bone loss.

And it’s not just energy: you also need adequate protein intake, as well as calcium and vitamin D to build bone.

4) Reproductive function requires energy.

One of the most common impacts low energy is menstrual dysfunction. Together with low bone density and disordered eating, this trio of symptoms is known as the female athlete triad. Adequate energy intake is key for menstrual function, including ovulation.

Interestingly, some studies have show impact to reproductive function in male athletes as well(2).

Summary of Low Daily Energy Outcomes

  • If you’re feeling lazy or unmotivated to train, eat well, or stay active, check in with how busy and overwhelmed you are.
  • Low daily energy can impact everything from performance to mood to your desire to take the stairs or walk after dinner. If you’re not sure how much you need to eat to fuel your performance in the gym, seek help from a sports nutritionist or registered dietitian.
  • Low energy availability in athletes is the underlying cause of the syndrome, Relative Energy Deficiency in Sport (RED-S). There may be impacts to performance, health, and well-being such as difficulties with digestion, mood, focus, bone health, and menstrual function.
close up of chicken and sweet potatoes in a glass container for more daily energy intake

Bottom line: If you want to become a better, faster, stronger version of yourself, you need energy.

Nutritionally, this requires you to eat much more than you probably think.

More energy and better recovery allow you to stay consistent and keep your intensity of training high.

This allows you to build muscle and strength.

And it is this muscle which allows you to burn fat.

As the renowned OG of sports nutrition, Dr. Susan Kleiner(3), puts succinctly, in order: eat more, gain energy, train harder, build muscle, burn fat. 

*Client names have been changed for privacy


  1. Wasserfurth, P., Palmowski, J., Hahn, A. et al. Reasons for and Consequences of Low Energy Availability in Female and Male Athletes: Social Environment, Adaptations, and Prevention. Sports Med – Open 6, 44 (2020).
  2. Mountjoy M, Sundgot-Borgen JK, Burke LM, et alIOC consensus statement on relative energy deficiency in sport (RED-S): 2018 updateBritish Journal of Sports Medicine 2018;52:687-697.
  3. Kleiner, S.M.  2018. The New Power Eating. Human Kinetics, Inc. 

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Steph Gaudreau

Hi, I'm Steph Gaudreau (CISSN, NASM-CPT)!

Nutrition and fitness coach for women, Lord of the Rings nerd, and depending on who you ask, crazy cat lady. My mission is to help you fuel for more: bigger muscles, strength, energy, and possibilities. We’ll do it with my signature blend of science, strategy…and a little bit of sass.


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