Inadequate Energy Provision in Sports, RED-S Syndrome

As per the IOC statement of 2005, the Trinity of Athletes was described as a combination of eating disorders and irregular menstrual cycles, leading to a decrease in endogenous estrogens and other hormones, which in turn affect low bone mineral density. The American College of Sports Medicine (ACSM) defined the trinity as a clinical entity referring to a relationship between three interrelated factors: energy availability (EA), menstrual disorder, and bone function and health. In 2007, scientific evidence and clinical experience suggested new perspectives in the development of the trinity, pointing to chronic energy deficiency resulting from an imbalance between energy intake in diet (EI) and the energy requirement for maintaining homeostasis, health, daily activities, growth, and training. This leads to an imbalance that affects a range of other changes, including metabolic rate, menstrual disorders, reduced immunity, protein synthesis, and mental health. Imbalances in energy metabolism also affect men. Therefore, the IOC committee modified the terminology and changed the trinity to relative energy deficiency in sport (RED-S).

Energy deficiency and poor nutrition in the context of RED-S can have serious consequences, impacting short-term or long-term health and physical fitness. Athletes who suffer from long-term low energy intake may be exposed to nutrient deficiencies (including anemia), chronic fatigue, as well as an increased risk of infections. Accompanying physiological and medical complications involve the cardiovascular, gastrointestinal, endocrine, reproductive, skeletal, and renal systems. Low energy intake also negatively affects lipid profiles and endothelial dysfunction, increasing the risk of cardiovascular episodes. Hormonal and metabolic irregularities caused by carbohydrate deficiency and RED-S contribute to reduced glucose utilization, fat metabolism, slowed metabolic rate, and decreased growth hormone production. Irregular or absent menstrual cycles can have a significant impact on emotions and cause anxiety, further negatively affecting the skeletal system. It is worth noting that peak bone mass occurs in women around the age of 19 and in men around the age of 20.5. Estrogens increase calcium uptake into the blood and bone deposition, while progesterone facilitates this action. Even subtle disruptions in the estrogen-progesterone balance, such as those seen in subclinical ovarian dysfunction with low energy availability, can cause changes in the skeletal system. In both men and women, testosterone has an anabolic effect and influences bones, promoting bone formation and calcium absorption. Low testosterone levels are associated with low bone mineral density in young men. Bone loss in these athletes may be irreversible. Changes in bone structure increase the risk of stress and fractures. RED-S also affects the nervous system - nutrient deficiencies increase the risk of stress and fractures in both sexes. In weight-dependent sports, extreme weight control methods (vomiting, diuretics, and laxatives) have unpleasant health consequences related to electrolyte imbalance and gastrointestinal problems caused by chronic vomiting. Additionally, taking supplements with diuretic effects can be risky in professional sports - they may contain substances banned by WADA.

In certain instances, nutritional counseling and dietary monitoring may not be sufficient interventions for physically active individuals or athletes who have experienced health complications related to inadequate energy levels. In specific situations, additional medical assistance from physicians or psychotherapists may be necessary for treating eating disorders. The therapeutic plan should take into consideration the individual's specific goals, diet, and training practices, as well as any other co-existing conditions. Nutritional management should be based on the significance of health, appropriate nutrition, and mental health in order to ensure a sustainable return to health. Treatment strategies for RED-S involve increased energy requirements and reduced physical activity or a combination of these two methods. The selection of the method depends on individual collaboration. One strategy involves introducing energy-rich supplements into the diet or consuming additional kcal in the form of meals and simultaneously reducing physical activity. Restoration of energy balance may occur after a few days or weeks and can initiate the reversal of certain negative health consequences. Determining the appropriate energy requirement for an individual with high energy expenditure can be challenging in many cases. It is recommended to gradually increase the energy requirement of meals by 300–600 kcal; the provided energy should be distributed throughout the day, including training sessions. It has been shown that a weight gain of 5–10% or 1–4 kg weight gain restores menstruation in women.

The recommendations for daily intake of carbohydrates and fats vary depending on the individual, their health condition, chosen discipline, daily effort, and previous dietary plans. The impact of exercises on the body should be taken into account when determining daily carbohydrate intake: technical exercises or low-intensity exercises: 3-5 g/kg body weight/day; moderate exercises (e.g. around 1 hour/day): 5-7 g/kg/day; endurance training (e.g. 1-3 hours/day of exercise with moderate or high intensity): 6-10 g/kg/day; extreme commitment to training (e.g. > 4-5 hours/day of exercise with moderate or high intensity): 8-12 g/kg/day. The body's protein requirements can range from 1.2 to 2 g/kg body weight/day, depending on periodic training plans, taking into account changes in the training schedule, such as sessions with higher frequency or intensity or new training stimuli. Fats should account for at least 20% of the energy requirement. Individuals with RED-S diagnosis often restrict their energy intake, which can lead to issues with the intake of micronutrients – particular attention should be paid to iron, vitamin D, and calcium. These nutrients are especially important for physically active individuals.

The inclusion of appropriate nutritional therapy in the treatment plan of individuals diagnosed with RED-S is essential for an effective return to health. In many cases, individuals affected by RED-S also require the assistance of other medical specialists and psychologists. The holistic approach is crucial for a full recovery of health and training. Many current publications discuss the potential risk to women. However, in recent years, there have been studies concerning young and adult men who also restrict their energy intake. Providing adequate education to both groups can prevent undesirable health consequences and long-term exclusion from sports.