For athletes, fueling is about eating enough for what your body needs. Underfueling is more common than most people realize with ~1 in 2 female athletes not eating enough to support health & performance (1) and and it can happen without any intention of restricting food. The problem? Underfueling can seriously impact your energy, recovery, performance and even your health.
You don’t have to track every calorie to know if you’re falling short. Your body gives you signals—subtle (and not-so-subtle) cues that it’s running on empty. Let’s break down some of the warning signs and simple ways to stay ahead of underfueling.
🚩 Signs You Might Be Underfueling
😴You’re Always Tired (Even After a Good Night’s Sleep)
If you wake up feeling like you’ve been hit by a truck even after eight hours of sleep, your energy intake might be too low. Your body needs fuel to repair and recharge overnight, and if you’re not eating enough, your recovery suffers.
😩Workouts Feel Harder Than Usual
Struggling to hit paces that used to feel easy? Fatiguing earlier in a session? Underfueling depletes muscle glycogen—the primary energy source for exercise—making workouts feel like a grind.
😋You’re Always Thinking About Food
Constantly dreaming about your next meal? Food preoccupation is a big red flag. Your brain prioritizes energy balance, so if you’re underfueling, it’ll try to get your attention by making food very interesting.
😒Your Mood is… Not Great
Irritability, anxiety, and low motivation can all be linked to inadequate energy intake. Your brain also runs on fuel, and when it’s not getting enough, emotional regulation can take a hit. Low carb intake can be a key contributor, too.
🤧You’re Getting Sick or Injured More Often
Frequent colds? Nagging injuries? Underfueling can suppress immune function and weaken bone and muscle tissue, increasing the risk of illness and overuse injuries.
🩸You’re Losing Your Period (or It’s Irregular)
Missing periods or irregular cycles can be a sign that your body isn’t getting enough fuel. This is a major marker of energy imbalance and can have long-term consequences for your health & performance.
🔗Learn more about the signs, symptoms and risks of chronic underfueling here.
✅ Easy Fixes to Stay on Top of Your Fueling Needs
💡 Add a Pre-Workout Snack: A quick carb + protein combo (like a banana with peanut butter) can help you train stronger and recover faster.
💡 Prioritize Recovery Meals: Within 30–60 minutes post-workout, aim for at least 30g of protein and carbs to replenish energy stores and kickstart muscle repair.
💡 Listen to Hunger Cues (Don’t Ignore It!): If you’re feeling hungry, that’s your body telling you it needs more. Don’t wait until you’re starving. Fueling consistently (every 3-4 hours) throughout the day helps prevent energy crashes, keeps hunger in check, and supports muscle recovery.
💡 Check Your Overall Intake: If you recognize multiple signs of underfueling, you might need to increase your total energy intake. Adding an extra snack or slightly larger portions can make a big difference.
💡 Work with a Sports Nutritionist: Not sure where to start? We can help you fine-tune your fueling strategy based on your unique training load and goals. Schedule a complimentary info call to learn how fuel smarter, feel better, and perform at your best.
Underfueling isn’t always obvious, but it is fixable. Pay attention to what your body is telling you—and give it the fuel it needs to perform and thrive.
References
(1) Heikura IA,. McCluskey WTP, Tsai M-. C, et al. Application of the IOC Relative Energy Deficiency in Sport (REDs) Clinical Assessment Tool version 2 (CAT2) across 200+ elite athletes. Br J Sports Med. 2025;59:24–35.
