Understanding RED-S in Recreational Athletes and How to Combat Under-Fuelling

Many high-performing women who juggle running, strength training, work, and daily life often find themselves unintentionally under-fuelling. This can lead to a condition known as Relative Energy Deficiency in Sport (RED-S), which is increasingly common not only in elite athletes but also in recreational ones. This post explains what RED-S is, why it happens, and how to recognize and address it to maintain both health and performance.

What is RED-S?

RED-S stands for Relative Energy Deficiency in Sport. It occurs when the energy a person consumes through food is insufficient to support the energy they expend through exercise and basic bodily functions. This energy shortfall affects many body systems, including metabolism, menstrual function, bone health, immunity, and cardiovascular health.

Unlike common misconceptions, RED-S is not just about being underweight or visibly thin. It can affect anyone who consistently consumes fewer calories than their body needs, regardless of their body size or shape.

Why Under-Fuelling Happens in Recreational Athletes

Many recreational athletes, especially women, fall into under-fuelling without realizing it. Here are some reasons why:

• Balancing multiple demands: Managing work, family, and training can make it hard to prioritize nutrition.

• Misunderstanding energy needs: Increased training volume raises energy requirements, but many don’t adjust their food intake accordingly.

• Desire to stay lean: The pressure to maintain a certain body composition can lead to intentional or unintentional calorie restriction.

• Lack of awareness: Early signs of RED-S are subtle and often mistaken for normal fatigue or stress.

  
  

The Role of Energy Availability and Hormones

Energy availability refers to the amount of energy left for the body’s physiological functions after accounting for exercise energy expenditure. When this availability drops too low, the body reduces energy spent on non-essential functions, including hormone production.

For women, this often means disruptions in menstrual cycles, which is a key warning sign of RED-S. Hormones like estrogen play a crucial role in bone health and overall wellbeing, so their reduction can lead to serious health issues.

Common Symptoms and Warning Signs

RED-S can manifest in various ways, often appearing suddenly and without clear cause. Some common symptoms include:

• Fatigue that doesn’t improve with rest

• Frequent injuries, especially stress fractures

• Stalled or declining performance despite training

• Mood changes and irritability

• Irregular or missed menstrual periods

  
  

Recognizing these signs early can prevent long-term damage and help athletes adjust their nutrition and training.

How Increased Training Volume Changes Energy Needs

When training volume increases, the body requires more fuel to recover and perform. For example, a runner adding extra miles or incorporating strength sessions will burn more calories and need more nutrients to repair muscles and maintain energy levels.

Failing to increase food intake accordingly leads to a negative energy balance, which can trigger RED-S. It’s important to track training load and adjust nutrition to match.

Breaking the Cycle of Under-Fuel, Overtrain, and Burnout

Many women get stuck in a cycle where under-fuelling leads to fatigue and injury, which then causes frustration and more intense training to "catch up." This cycle often ends in burnout or long-term health problems.

To break this cycle:

• Prioritize nutrition: Fuel workouts with balanced meals and snacks.

• Listen to your body: Rest when needed and avoid pushing through persistent fatigue.

• Seek professional advice: A dietitian or sports nutritionist can help tailor your eating plan to your training.

  
  

How to Fuel Training Properly Without Sacrificing Body Composition

Proper fueling does not mean losing control over body composition. Instead, it means eating enough to support your activity while maintaining your goals. Here are some tips:

• Focus on nutrient-dense foods: Whole grains, lean proteins, healthy fats, fruits, and vegetables.

• Eat regularly: Don’t skip meals, especially around workouts.

• Include carbohydrates: They are the primary fuel for endurance and strength training.

• Hydrate well: Dehydration can worsen fatigue and performance.

• Adjust portions: Increase intake on heavier training days and reduce slightly on rest days.

  
  

When to Seek Help

If you experience persistent fatigue, frequent injuries, or menstrual irregularities, it’s important to consult a healthcare professional. Early intervention can prevent serious complications like bone loss or hormonal imbalances.

Understanding RED-S and its impact on recreational athletes is essential for maintaining long-term health and performance. If you train hard but feel constantly tired or injured, consider your energy intake and how it matches your training demands. Proper fueling supports your body’s ability to perform and recover, helping you stay strong and healthy.

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