How to Tell If You’re Eating Enough to Support Your Endurance Sport Performance
Endurance athletes—including triathletes, swimmers, and long-distance runners—have some of the highest energy demands in sport. Proper nutrition is essential not only to fuel long training sessions and races but also to support recovery, prevent injury, and maintain long-term health. Yet, under-fuelling is a common issue that can undermine your endurance goals.
Here are key signs to help you determine if you’re meeting your body’s energy needs for optimal endurance performance:
1. Persistent Fatigue and Low Energy
If you’re constantly feeling drained despite adequate rest, it’s a red flag that your energy intake may be too low to sustain your prolonged training and recovery. Energy in our diet comes from our key macronutrients carbohydrates, proteins and fats.
2. Unintended Weight Loss or Difficulty Maintaining Race Weight
Endurance training burns significant calories. Unexpected weight loss or struggling to keep your ideal racing weight often indicates negative energy balance.
3. Increased Illness or Injury Risk
Frequent colds, infections, or recurring injuries can result from under-fuelling, which weakens your immune system and delays tissue repair.
4. Disrupted Menstrual Cycle (for Female Endurance Athletes)
Missed or irregular periods are a serious sign of Relative Energy Deficiency in Sport (RED-S), a condition linked to insufficient energy intake relative to training loads.
5. Performance Plateaus or Declines
If your endurance times stall or worsen despite consistent training, inadequate nutrition could be limiting your body’s ability to adapt and improve.
6. Mood Changes and Trouble Concentrating
Endurance training places demands on both body and mind. Nutritional shortfalls can cause irritability, mood swings, and reduced mental focus during training and competition.
7. Sleep Disturbances
Poor nutrition can disrupt your sleep quality—critical for muscle repair, glycogen restoration, and overall recovery.
How to Ensure You’re Fueling Adequately for Endurance Success
Monitor Your Energy Intake & Get Feedback from a Sports Dietitian: Track your food and fluid consumption to ensure it matches your high training demands. Get personalised guidance tailored to your training volume and race goals.
Prioritise Post-Training Recovery Consistently: Consume quality carbohydrates, adequate protein and plenty of colour (fruits/veggies) within 30–60 minutes of exercise to replenish energy stores and support muscle repair.
Stay Hydrated: Replace fluids and electrolytes lost through sweat during long sessions, especially in warm conditions. Make sure you have drank 1.5x your body weight loss in fluid during exercise over the couple of hours finishing training.
Listen to Your Body: Pay attention to hunger, energy levels, and mood as changes to these may signal your nutrition intake needs tweaking.
If you’re an endurance athlete in Sydney or training remotely, and want to optimise your nutrition for sustained performance and health, I’m here to help. I’m Ashleigh Brunner, Advanced Sports Dietitian specialising in endurance sports.