10 Signs You're Underfueling (Even If You Think You're Not)

You train hard. You eat "healthy." You think you're doing everything right.

But something's off. You're tired, you're not improving, and you can't figure out why.

The culprit might be underfueling — and you might not even know it.

Underfueling (low energy availability) occurs when you consume fewer calories than you burn through training and daily living.

This leaves your body in an energy deficit, forcing it to downregulate systems that aren't immediately essential for survival — including performance, recovery, and immune function.

• 1. Persistent fatigue despite adequate sleep
• 2. Declining performance despite hard training
• 3. Frequent illness or slow recovery from illness
• 4. Irregular or absent periods (female athletes)
• 5. Mood changes: irritability, anxiety, or depression
• 6. Difficulty concentrating or brain fog
• 7. Obsessive thoughts about food and weight
• 8. Cold intolerance or feeling cold all the time
• 9. Slow healing of injuries or frequent injuries
• 10. Difficulty maintaining race weight or unintended weight loss

Chronic underfueling leads to RED-S (Relative Energy Deficiency in Sport), which affects:

• Metabolic rate (body slows down to conserve energy)
• Bone health (increased fracture risk)
• Immune function (more illness)
• Protein synthesis (worse recovery)
• Hormonal function (menstrual dysfunction, low testosterone)
• Cardiovascular health

Track your intake for one week and compare to your training load:

• Aim for 30–40 kcal/kg of body weight on high-training days
• Include adequate carbs to support glycogen needs
• Distribute protein across 4–5 meals (1.2–1.4 g/kg)
• Note any symptoms from the list above

• Increase calorie intake gradually (200–500 kcal/day)
• Prioritize carbohydrates around training
• Include protein at every meal
• Reduce training load if needed
• Seek guidance from a sports dietitian if symptoms persist

Consult a healthcare provider if you experience:

• Absent periods for 3+ months
• Persistent mood changes
• Unexplained injuries or slow healing
• Difficulty eating enough despite trying

MAVR tracks your intake against training load to identify underfueling early:

• Compares daily calorie intake to workout demands
• Flags when intake falls below minimum thresholds
• Suggests adjustments to prevent energy deficit
• Monitors trends over time to catch chronic underfueling