What do Veronica Ewers, Mary Cain, Lionel Sanders, and Jake Riley have in common besides being at the top level of their sports? They have faced the challenges associated with Relative Energy Deficiency in Sport (RED-S) and publicly discussed their experiences with RED-S. However, RED-S is not only reserved for elite level athletes. It can affect the everyday athlete as well. In this blog, we will discuss what RED-S is, who can experience it, how to recognize the warning signs, and what can be done to prevent it. To help us better understand RED-S, we chatted with Sophia Jones, RDN, LD. In addition to being an ultrarunner, Sophia has vast knowledge working with individuals and athletes addressing eating disorders, disordered eating, RED-S, and performance nutrition.
What is RED-S? How is it different from the female athlete triad and overtraining?
Sophia: RED-S occurs when an athlete does not take in enough energy (calories) to support both their training and their basic physiological functions. This creates low energy availability, which can result from factors like increased training without increased fueling, nutrition misinformation, disordered eating or eating disorders, and body image concerns.
RED-S can impair multiple body systems, including growth and development, reproductive health (missed or irregular periods, low libido), bone health (stress fractures, early osteoporosis), immunity (frequent illness, slow healing), metabolism and digestion (gastroparesis, cramping, alterations in bowel habits), cardiovascular health (low heart rate, dizziness, potential long-term heart damage), and mental health (depression, anxiety, irritability, and reduced cognitive function). Additionally, it has negative effects on athletic performance, including decreased endurance, decreased power, delayed recovery, poor training adaptations, and decreased motivation. The graphics below are from the updated 2023 IOC Consensus Statement on RED-S and detail the plethora of physiological and performance based consequences of RED-S.
The Female Athlete Triad is a narrower, older model that focuses on three issues in female athletes: low energy availability (with or without disordered eating), menstrual dysfunction (irregular periods or amenorrhea) and low bone density (osteopenia or osteoporosis). RED-S is the updated, broader framework released by the International Olympic Committee in 2014 (updated in 2018 and 2023) that applies to all genders and includes many more health and performance effects. Overtraining and RED-S look very similar and have a lot of symptomatic overlap, but they are not the same thing. Overtraining syndrome is traditionally described as a chronic imbalance between intense training load and insufficient recovery. It predominantly affects the central nervous system and it can be difficult to diagnose because there are few clear biomarkers. However, research has shown that most athletes labeled as “overtrained” may also be underfueling. In fact, in over 80% of studies on overtraining, athletes had low energy or low carbohydrate availability during periods of performance decline, producing the same hormonal, immune, and recovery problems seen in RED-S. This means many cases of “overtraining syndrome” could actually be misdiagnosed RED-S, where the body isn’t breaking down from excessive training, but from insufficient fuel to support the training.
Carbs Fuel TLDR: RED-S is a condition where there is insufficient energy available for the body to properly support basic physiological functions and training, resulting in negative health outcomes. The RED-S framework addresses all genders and is broader in coverage, superseding the Female Athlete Triad, an older and more limited model focused only on females. While RED-S and overtraining may share similar symptoms, RED-S is a result of an energy imbalance while overtraining is a result of imbalanced training and recovery.
Can RED-S occur in recreational and professional athletes? Is it more common in recreational or professional athletes?
Sophia: RED-S can absolutely occur in both recreational and professional athletes. I would argue that RED-S is likely more common in recreational athletes than in professional athletes. While elite athletes may train more and/or at higher relative intensities, they also usually have access to sports dietitians, medical teams, and structured fueling and training plans. Recreational and sub-elite athletes, on the other hand, often train just as hard (comparatively) while juggling full-time jobs, family, and limited nutrition/medical support. This means they are more likely to underfuel, follow misinformation, or unintentionally restrict intake, which makes RED-S both more common and more likely to go undiagnosed in this group.
Carbs Fuel TLDR: RED-S is non-discriminant. It can impact any individual whether they are a recreational or professional athlete.What are warning signs RED-S and does RED-S manifest differently depending on the individual?
Are women or men more susceptible? Is RED-S in women and men manifested differently?
Sophia: While RED-S affects both men and women, most research has historically focused on female athletes because females have higher rates of RED-S. The research community continues to emphasize the need for more studies on RED-S and low energy availability in men. Interestingly, current evidence suggests that women may experience symptoms when energy availability drops below 30 kcal/kg fat-free mass/day, while men can often sustain lower levels (~9-25 kcal/kg fat-free mass/day) before symptoms arise. Low energy availability in men can still disrupt hormones, metabolism, immunity, bone health, performance, and lean body mass. Emerging signs in men include low libido and fewer morning erections. Overall, the physiological impacts of RED-S are similar across sexes, though the exact thresholds and severity of symptoms can differ.Does age impact the susceptibility to RED-S?
Carbs Fuel TLDR: Age does influence the likelihood of developing RED-S, especially for younger individuals whose bodies need significantly more energy to support both puberty and training. That said, adult athletes are still susceptible to RED-S if energy availability is too low.
How does an individual recover from RED-S?
Carbs Fuel TLDR: A comprehensive and individualized approach with guidance and support from a team of professionals provides the best chance for an individual to recover from RED-S. Restoring energy balance through education, psychological support, and sustainable health habits is the key to recovery and a safe return to sport.
How can you prevent RED-S?
Carbs Fuel TLDR: Education and awareness is the best way to prevent RED-S. Through proper education of healthy nutrition habits and addressing the psychology behind sport performance and body image in sport, individuals can have the knowledge to address behaviors that may lead to RED-S.
Lately, there has been significant focus on the importance of properly fueling workouts. What is the influence of intra workout fueling and the development of RED-S? And does the type of fuel (i.e. carbohydrates, fats, protein) I use during training matter?
The type of fuel matters. Before and during training, the priority should be simple, rapidly absorbed carbohydrates - low fiber, low fat, and low protein - to provide fast energy and minimize GI distress. Protein and fat generally do not meaningfully support training performance or RED-S prevention during most workouts. The main exception is ultra-endurance events (>6 hours), where small amounts of fat and protein from real foods can help with satiety, palatability, and meeting very high energy needs while preventing excessive muscle breakdown.
Evidence-based carbohydrate targets during training are:- <2.5 hours: 40–60 g/hr (single-source carbs, ie glucose or maltodextrin)
- 2.5 - 5 hours: 60–90 g/hr (multiple transportable carbs such as glucose + fructose in ~2:1 ratio)
- >5 hours: 60–90+ g/hr using multiple transportable carbs (2:1 glucose:fructose (60g/hr) or ~0.8:1 glucose:fructose (>90g/hr)), with small amounts of real food throughout for palatability and variety
Carbs Fuel TLDR: Fueling during workouts is one of the key levers used to reduce the energy deficits that occur during training. Ensuring that you fuel properly with carbohydrates before, during, and after training is key to steering clear of RED-S. While fats and protein are key macronutrients, it is best to save these for when you are not training.
Summary
Sophia Jones, RDN, LD: https://savoredjourneyllc.com
Sources:Mountjoy M, Ackerman KE, Bailey DM, Burke LM, Constantini N, Hackney AC, Heikura IA, Melin A, Pensgaard AM, Stellingwerff T, Sundgot-Borgen J, Torstveit MK, Jacobsen AU, Verhagen E, Budgett R, Engebretsen L, Erdener U. International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2023. doi: 10.1136/bjsports-2023-106994.
Stellingwerff T, Heikura IA, Meeusen R, Bermon S, Seiler S, Mountjoy ML, Burke LM. Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities. Sports Med. 2021 Nov;51(11):2251-2280. doi: 10.1007/s40279-021-01491-0. Epub 2021 Jun 28. PMID: 34181189.Cabre HE, Moore SR, Smith-Ryan AE, Hackney AC. Relative Energy Deficiency in Sport (RED-S): Scientific, Clinical, and Practical Implications for the Female Athlete. Dtsch Z Sportmed. 2022;73(7):225-234. doi: 10.5960/dzsm.2022.546. Epub 2022 Nov 1. PMID: 36479178; PMCID: PMC9724109.
