FSHP Academy
Sports Nutrition — all lessons

Module 1: Foundations of Sports Nutrition

Energy systems and metabolism for nutritionMacronutrients and athletic performanceMicronutrients and hydration essentials

Module 2: Nutrition for Training & Competition

Pre-, intra- and post-workout nutrition strategiesFuelling for endurance vs strength/power sportsCompetition-day meal planning

Module 3: Body Composition & Weight Management

Balancing muscle gain and fat lossSafe weight-cutting practices for athletesNutrition for injury prevention and recoveryEnergy availability and RED-S

Module 4: Supplements & Ergogenic Aids

Evidence-based supplements (creatine, caffeine and others)Avoiding banned substances and doping risks

Module 5: Practical Applications

Creating individualised nutrition plansSports nutrition case studies

Energy availability and RED-S

Low energy availability and Relative Energy Deficiency in Sport (REDs) — definitions, health and performance consequences, screening and prevention.

Advanced Evidence: Established consensus 3 min read Reviewed 2026-10-31 Status: draft

Learning objectives

  • Define energy availability and calculate it
  • Describe health and performance consequences of REDs
  • Recognise warning signs and risk factors
  • Refer and support athletes appropriately

Before this lesson

Why this matters

Underfuelling is common in sport — sometimes deliberate, often unintentional. Its effects reach bones, hormones, immunity, mental health and performance.

Energy availability

EA = (energy intake − exercise energy expenditure) ÷ FFMExpressed in kcal per kg fat-free mass (FFM) per day.

Example: 2,200 kcal intake − 900 kcal exercise = 1,300 kcal; ÷ 48 kg FFM ≈ 27 kcal/kg FFM/day. Historically, values below ~30 kcal/kg FFM/day were used as a threshold for low energy availability in women, but the 2023 IOC consensus emphasises that problematic low energy availability is about severity, duration and individual response, not a single cut-off [mountjoy2023].

REDs

Relative Energy Deficiency in Sport (REDs) describes impaired physiological and psychological function caused by problematic low energy availability [mountjoy2023]. Consequences include:

  • Menstrual dysfunction and low testosterone
  • Low bone mineral density and bone stress injuries
  • Reduced metabolic rate, iron and gastrointestinal problems
  • Increased illness, mood disturbance
  • Decreased training response, strength, endurance and coordination

REDs affects athletes of all sexes and can occur at normal body weight.

Risk factors

Weight-sensitive or aesthetic sports, high training volumes, restrictive eating, rapid weight cutting, lack of nutrition knowledge, and food insecurity.

Common mistakes and misconceptions

Case study

A 19-year-old male cyclist has had two illnesses and a tibial stress fracture in a year and reports low energy. His coach refers him to a sports doctor; assessment indicates low energy availability. A dietitian-led plan increases intake around training; performance and wellbeing recover over months.

Further learning: video lessons

Video links are only marked “verified” after a human has watched them. Unverified entries open a YouTube search for that channel and topic rather than a guessed link.

Introductory needs verification — opens a YouTube search

REDs explained

IOC / BJSM (search)

You will understand: what REDs is and why it matters

Why: From the consensus authors.
Technical needs verification — opens a YouTube search

Low energy availability in male athletes

sports medicine educators (search)

You will understand: REDs beyond the female athlete triad

Why: Broadens awareness.

Knowledge check

Knowledge check · 0/5

1. Energy availability is calculated as…

Answer B. Energy left for other body functions.

2. REDs can affect…

Answer B. The IOC 2023 consensus emphasises all athletes.

3. Which is a possible sign of REDs in a female athlete?

Answer B. Menstrual dysfunction is a key indicator.

4. Which sign might suggest REDs in a male athlete?

Answer B. Hormonal and other systemic effects.

5. The trainer’s role with suspected REDs is to…

Answer B. Multidisciplinary care is required.

Short-answer & application questions

  1. Calculate EA for an athlete eating 2,200 kcal, expending 900 kcal in training, with 48 kg FFM.
  2. List risk factors and warning signs of REDs in your sport.
  3. How would you raise concerns with an athlete you suspect has REDs?

Key takeaways

  • Energy availability = energy intake − exercise energy expenditure, per kg fat-free mass.
  • Problematic low energy availability impairs many systems: hormones, bone, metabolism, immunity, mental health and performance.
  • REDs affects athletes of all sexes and can occur without low body weight.
  • Early recognition and multidisciplinary support (doctor, dietitian, psychologist) are key.

Connected topics

sports nutrition

Safe weight-cutting practices for athletes

womens health

Understanding the menstrual cycle

anatomy

Bone structure, remodelling and adaptation to loading

lifestyle nutrition

Non-scale victories and body image

References

  1. Mountjoy M, Ackerman KE, Bailey DM, et al. (2023). 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine, 57(17):1073–1097. doi:10.1136/bjsports-2023-106994 Guideline check pending
  2. Thomas DT, Erdman KA, Burke LM (2016). American College of Sports Medicine joint position statement: nutrition and athletic performance. Medicine & Science in Sports & Exercise, 48(3):543–568. doi:10.1249/MSS.0000000000000852 Position stand check pending

Educational content only — not medical advice. Consult a qualified clinician for diagnosis or treatment.