Amy Stephens
MS, RDN, CSSD, CEDS
Licensed dietitian
specializing in sports nutrition
and eating disorders
How to know when your fueling plan is working
- By Kate Cochran, Nutrition Intern and NYU XC Athlete
- Reviewed by Amy Stephens, Sports Dietitian
Fueling properly for your sport can feel both straightforward and surprisingly complex. For endurance runners, a solid baseline is three balanced meals focused on carbs for energy, protein for recovery, and fats for satiety, with snacks in between.
I sometimes find that even when I’m consciously trying to eat enough to feel strong, I am still hungry at times. It can feel frustrating, like no matter how much I eat, it’s never quite enough. Instead of focusing solely on calorie counting, there are other effective ways to assess whether you’re eating enough. Calorie estimates can be helpful as a general guide, but relying too heavily on them can shift attention away from your body’s natural hunger and fullness cues.
When your fueling plan is working, it shows — and when it’s not, the under-fueling signs show up in many areas of your life. Fueling isn’t just about food; it’s the foundation for how you feel, perform, and recover.
As an athlete, you’ll know your fueling plan is working when you feel strong and focused, and recover well. Your body gives you signals—through energy levels, performance, and how you feel day to day. The key is learning to tune in and respond to those signals.
Signs that your fueling plan is working:
Energy & Performance
You feel energized not just during workouts, but throughout the day – no mid-session crashes or post-training slumps. Not being able to get through daily tasks, school, or work is a sign that you may be under-fueled.
You’re meeting or progressing toward your strength, speed, endurance, or intensity targets consistently and without excessive fatigue.
You’re performing at a strong, stable level in training and competition.
Recovery
You experience less muscle soreness and bounce back relatively quickly after workouts which is a sign your body is getting the nutrients it needs.
You don’t have lingering fatigue or excessive delayed-onset muscle soreness (DOMS).
You wake up feeling refreshed, alert, and ready to train– not groggy, drained, or sluggish. When the body isn’t receiving enough energy, it can lead to restless and interrupted sleep. Underfueling can affect blood sugar regulation and hormone balance, both of which are crucial for restful sleep.
Mental Focus
- You’re able to stay sharp, focused, and present – especially during long sessions.
- You experience minimal brain fog, irritability, or mood swings. These are often signs your brain isn’t getting enough fuel (especially carbs).
- You feel motivated and emotionally steady – not burned out, stressed, or overly reactive. Proper fueling supports your nervous system and helps you stay consistent over time.
Hunger & Cravings
- Your hunger feels balanced and predictable – not marked by extreme spikes or constant fluctuations.
- You do not experience frequent sugar or carbohydrate cravings which may be a sign that your macronutrient balance is off (not enough protein & fats).
- You’re eating enough to feel satisfied without feeling bloated, overly full after only eating a small amount, or persistently hungry.
Lab & Biomarker Indicators
- Ferritin levels between 40-100 ng/dl is optimal. Low levels can result in fatigue, decreased stamina, and poor performance.
- B vitamins (B12 between 200–900 pg/mL & Folate between 3-17 ng/mL) – low levels can contribute to fatigue, brain fog, or poor adaptations to training.
- Vitamin D between 30-50 ng/mL is ideal for athletes. Optimal levels help reduce injury risk and improve recovery.
- Resting heart rate – having an elevated RHR over time may suggest overtraining or under-fueling. Additionally, an abnormally low RHR can also mean under-fueling. Everyone’s normal RHR is different, so it’s optimal to track yours over time using a wrist heart rate monitor to understand your patterns. What is high for someone might be low for you, and vice versa. Always consult with your doctor if you experience either of these patterns.
- Cortisol – high cortisol (stress hormone) can indicate chronic stress which can come from not fueling enough to meet your needs.
- Sex Hormones (estrogen, testosterone) – inadequate fuel can disrupt hormone production, impact bone health, mood, libido, and menstrual cycles in female athletes.
It can be difficult to distinguish between feeling tired from high training volume and feeling drained because you’re not fueling enough to meet your body’s needs. If you’re experiencing several of the symptoms mentioned above, it’s worth taking a closer look at your nutrition and whether it’s truly supporting your training and daily life.
Working with a sports dietitian can be incredibly helpful — they can assess your typical day or week of eating and guide you on where you’re meeting your needs and where there’s room for improvement.