The Risks of Underfueling your training
- Grace Downer
- Apr 6
- 5 min read
There is a mindset that shows up a lot in fitness spaces. Train more. Eat less. Push harder. Stay disciplined.
It sounds tough. It sounds effective. It is also one of the fastest ways to stall progress and run your body into the ground.
More training does not equal better results. Less food does not equal faster results.
If your goal is to get stronger, improve performance, and actually feel good doing it, fueling your body is not optional. It is foundational.
What does “underfueling” actually mean?
Underfueling happens when your energy intake does not match the demands you are placing on your body.
This is not just about calories in a general sense. It is about energy availability. That is the amount of energy left over for your body’s basic functions after accounting for exercise.
Your body has a long list of priorities beyond your workouts. Hormone production, brain function, immune health, recovery, and cellular repair all require energy.
When there is not enough to go around, your body starts making tradeoffs.
Performance is often one of the first things to suffer. Long-term health is not far behind.
Why more training and less food backfires
When you consistently train hard without fueling enough, your body shifts into a conservation mode.
Instead of building and adapting, it starts protecting.
Recovery slows down
Muscle growth is limited
Strength gains stall or decline
Injury risk increases
At a certain point, you are no longer building fitness. You are just accumulating stress.
This is why more is not always better. Training only works if your body has the resources to adapt to it.
The hormonal toll of underfueling
Chronic low energy availability disrupts the endocrine system. Hormones that regulate metabolism, stress, reproduction, and recovery all start to shift.
Research shows that insufficient energy intake can lead to reductions in key hormones such as estrogen, testosterone, and thyroid hormones, while increasing stress hormones like cortisol¹.
For women, the impact can be especially harsh.
Low energy availability is strongly linked to menstrual dysfunction, including irregular cycles or complete loss of a period. This is not just a reproductive issue. It is a sign that the body does not have enough energy to support normal physiological function².
Over time, this can affect bone health, increasing the risk of stress fractures and long term bone density loss.
This cluster of issues is often discussed under the umbrella of Relative Energy Deficiency in Sport, or RED-S. It highlights how widespread the effects of underfueling can be across multiple systems in the body³.
For men, hormonal disruption still occurs. Testosterone levels can drop, recovery suffers, and performance declines. It is just often less talked about.
The subtle signs you might be missing
Underfueling does not always show up as dramatic weight loss or obvious burnout right away. It often creeps in.
If you are seeing consistent patterns like these, your body is likely underfueled:
You feel chronically tired despite getting good, consistent sleep
You are experiencing increased hair loss
You are often cold, especially when others feel comfortable or warm
Your menstrual cycle becomes irregular or disappears
Your strength numbers plateau or start declining
Your power output feels flat, even when you are trying to push
These are not random inconveniences. They are signals.
Your body is telling you it does not have what it needs.
Performance suffers before most people realize it
One of the biggest misconceptions is that eating less will automatically improve body composition and performance.
In reality, chronic underfueling often leads to the opposite.
Without enough energy:
Training intensity drops
Volume becomes harder to sustain
Recovery between sessions is compromised
Over time, this leads to stagnation. You are working just as hard, if not harder, but getting less in return.
Well-fueled athletes are able to train harder, recover faster, and adapt more effectively. That is what drives progress.
Fueling is part of the training plan
It helps to reframe how you think about food.
Food is not something you earn after a workout. It is part of what allows the workout to be effective in the first place.
Carbohydrates support training intensity and replenish glycogen. Protein supports muscle repair and growth. Fats play a key role in hormone production.
When you consistently meet your body’s needs, everything works better.
Energy levels stabilize
Strength and performance improve
Recovery becomes more efficient
Hormonal health is supported
The bottom line
If you are training hard, you need to fuel accordingly. There is no workaround for that.
More training is not better if you cannot recover from it. Less food is not better if it compromises your health and performance.
The goal is not to do the most. The goal is to do what works.
If your body is sending signals that something is off, listen to them. Adjust your intake. Support your training.
Progress comes from the combination of stress and recovery. Fueling is what makes that equation work.
So eat yo’ dang food! (and sign up for Coach Kayla’s new Nutrition Consultation if you need a little guidance! Information below.)-Coach Grace
Footnotes
Chronic low energy availability has been shown to alter endocrine function, including reductions in sex hormones and thyroid hormones, alongside increases in cortisol.
Menstrual dysfunction is a well documented consequence of insufficient energy availability in active women and is a key clinical indicator of physiological disruption.
Relative Energy Deficiency in Sport (RED-S) describes the broader syndrome of impaired physiological function caused by low energy availability.
Works Cited
Mountjoy, Margo, et al. “The IOC Consensus Statement: Beyond the Female Athlete Triad Relative Energy Deficiency in Sport (RED-S).” British Journal of Sports Medicine, vol. 48, no. 7, 2014, pp. 491–497.
Loucks, Anne B. “Energy Availability, Not Body Fatness, Regulates Reproductive Function in Women.” Exercise and Sport Sciences Reviews, vol. 31, no. 3, 2003, pp. 144–148.
De Souza, Mary Jane, et al. “2014 Female Athlete Triad Coalition Consensus Statement on Treatment and Return to Play.” British Journal of Sports Medicine, vol. 48, no. 4, 2014, pp. 289.
Coach Kayla is happy to introduce her nutrition coaching sessions! Underfueling is a thing of the past and she is here to help.
These are 60 minute 1:1 consultations held in person or via video call to help you go over your current health habits, set your goals and come up with a plan that is tailored specifically to you.
Gaining knowledge and understanding about your body, what fuels you and how to feel your best, is right at your finger tips.
Coach Kayla specializes in the biology of nutrition and digestion, as well as the psychology of eating. As a Certified Behavioral Change Specialist, she focuses on helping you actually stick with a program. Using personalized, psychology-based strategies, she guides you through goal setting, accountability, mindset shifts, and overcoming obstacles so the changes you make feel realistic, sustainable and built to last.
These are not prescribed meal plans (those don’t work and it’s actually illegal), but instead a personalized approach that teaches you how to build habits, makes informed choices, and create a way of eating that fits your lifestyle for the long term. Reach your goals in the gym and in the kitchen this year!
-Coach Kayla
B.S. Food and Nutrition May 2026
Certified Nutrition Specialist 2014
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