Special diets or food restrictions have been recognized in the athletic population.1–3 In our original 1000 patient study, about one-quarter (23.4%) of female athletes reported restrictive diets. The most common diets were plant-based diets (vegan, vegetarian, and pescatarian) and elimination diets (gluten-free, low-carbohydrate, and low-dairy diets).
Plant-based diets may be differentiated based on their restriction of certain food groups.2 A pescatarian diet excludes meat and poultry but includes fish, dairy and eggs; a lacto-ovo vegetarian diet excludes meat, poultry, and fish, but includes eggs and dairy; a vegan diet excludes all meat, poultry, fish, eggs, and dairy.2 Different types of plant-based diets are described in Table 5. Of the athletes following only one diet (n = 133), 22.5% were vegetarian, 6.7% were vegan, and 4.5% were pescatarian. Plant-based diets have been linked to lower body mass index (BMI) and decreased risk of chronic disease, such as hypertension, diabetes, and obesity.2,20 However, these plant-based diets with high fiber content may also lead to early satiety and appetite blunting. These effects, in turn, can cause low energy intake and lead to low EA and its associated health and performance consequences.2,21 In addition, individuals practicing plant-based diets who do not consume dairy products or fish may be deficient in vitamin D, which is vital in maintaining adequate bone health.2,20−22
Table 5
Different types of plant-based diets.2
| Avoid meat/poultry | Avoid fish | Avoid eggs/dairy |
Vegan | X | X | X |
Vegetarian | X | X | |
Pescatarian | X | | |
A gluten-free diet restricts foods that contain the protein gluten, commonly in wheat, rye, or barley. Gluten-free diets are clinically indicated in managing gastrointestinal symptoms in patients who have celiac disease or non-celiac gluten sensitivity.2,3 Other common forms of elimination diets include low-carbohydrate and low-dairy diets, which restrict the intake of sugars/starches and milk-derived products, respectively. Low-carbohydrate diets have been around for decades; however, this dietary practice remains poorly defined. Individuals adhering to a low-carbohydrate diet may vary from simply avoiding these food groups, reducing the amount of daily carbohydrate intake (< 100 g/day), to severely restricting the amount of daily carbohydrate intake (< 50 g/day) to induce ketosis.23,24 In addition to medical indications or health and weight management benefits, popular trends initiated by professional or high profile athletes have also driven young athletes to participate in specific diets despite the absence of scientific evidence of performance benefits.3–5 Recent studies have shown that the majority of athletes practicing gluten-free diets have chosen to do so based on self-diagnosis, and despite lacking substantial evidence to support performance benefits, there has been an increase in the prevalence of non-celiac, non-gluten sensitive athletes adopting a gluten-free diet in attempt to optimize health and enhance athletic performance.3 Based on our study, there were 133 athletes who reported following only one diet, of which 19 (14%) followed a gluten-free diet, while 39 (29%) athletes followed a low-carbohydrate diet, and 30 (22.5%) athletes followed a low-dairy diet, without reporting any clinical indications. Gluten-free diets may be associated with suboptimal intake of carbohydrates and protein and can lead to micronutrient deficiencies (e.g., B vitamins, calcium, vitamin D, iron, and potassium), while low-dairy diets may be deficient in vitamin D and fat.2,3 Recommended macronutrient intake for female athletes range from 3–10 g/kg of the athlete’s body weight per day for carbohydrates, 1.2-2.0 g/kg/day for protein, and 20–35% of total kcal/day for fat.2 Athletes who fail to consume sufficient levels of these macronutrients may be at risk for RED-S; high-risk consequences specifically include impaired glycogen and muscle protein synthesis and bone remodeling, which may affect how athletes recover from exercise and their overall bone health.2
Previous studies have found a positive correlation between special diets and disordered eating.25–30 Specifically, patients diagnosed with anorexia nervosa have a higher prevalence of practicing vegetarianism at some point in their lives compared to the general population.27,28 Although there may be many reasons for special dietary practices, researchers have suggested that adherence to dietary restrictions may be used as a socially acceptable way to disguise disordered eating habits or behaviors.25,26 Restrictive dietary adherence amongst athletes is recognized as a risk factor for low EA and its subsequent RED-S health and performance-related consequences.4–6 However, we are unaware of any studies that have examined the relationship between specific diets and DE in the athletic population. Our study shows that of the 165 non-medically indicated diet-adherent athletes, 67.9% responded positively to ≥ 1 of the 3 ED/DE screening tools compared to 41.8% of the non-diet-adherent athletes (p < 0.0001).
ED/DE are more prevalent among athletes compared to their non-athletic peers.4–7 Peak onset is usually around puberty or adolescence (15–19 years old)11 due to the combination of biological and psychosocial changes that occur, which results in issues with body dissatisfaction, self-esteem, and mood.10 Objective information, such as low weight and BMI, may not be reliable among athletes due to their increased muscle mass, wherein energy deficient athletes can present with normal BMIs.4,7 Indeed, in our parent study, the inadequate EA group had a higher BMI than the adequate EA group.17 In the present study, however, we found an association between athletes reporting specific dietary practices and responding positively to ED/DE screening tools. Athletes who practiced vegetarian, vegan, low-carbohydrate, low-dairy, or ≥ 2 diets were more likely to respond positively to ≥ 1 ED/DE screening tool when compared to athletes without dietary restrictions. In terms of plant-based diets, vegan and vegetarian athletes who avoided more food groups were found to have a stronger association with responding positively to ED/DE screening tools, in contrast to athletes who practiced a pescatarian diet. Additionally, we found that individual athletes screened positively on some ED/DE screening tools and negatively on others, highlighting that it is may be clinically important to ask athletes about eating behaviors with various questions, framing the questions slightly differently to detect ED/DE.
Early detection of ED/DE among athletes is highly recommended to facilitate prompt treatment and prevention of health and performance-related consequences,4,31 such as menstrual dysfunction, impaired bone health and metabolism, increased injury risk, decreased endurance, performance, and coordination.12,17,32−34 The findings in this study may help bridge the gap in recognizing athletes at risk for developing ED/DE. The presence of specific dietary practices in female athletes should urge healthcare providers to consider further evaluation through validated ED/DE questionnaires even before the presence of subjective (e.g., desire to lose weight, body image dissatisfaction) or objective findings (e.g., low weight/BMI, oligomenorrhea) that are commonly used to diagnose ED/DE. Applying this in clinical practice may encourage healthcare providers to address behaviors linked to ED/DE in athletes, discuss their health implications, and offer access to appropriate resources, including nutritional and psychological support. Management of ED/DE in the athletic population requires a thorough evaluation and an interdisciplinary approach that focuses on patient-centered care.2,7,35 A registered dietitian who is experienced in treating athletes with ED/DE may help with managing nutritional adjustments, safe and effective supplementation, and monitoring of energy intake.2,7,31,35 In our study, the gluten-free diet for celiac disease and dairy-free diet for lactose intolerance were the most common reasons why female athletes follow special diets due to medical indications. In these cases, it is important for healthcare providers to educate these athletes regarding the possible macronutrient and micronutrient deficiencies associated with these diets that can lead to low EA, and guide them towards proper adjustments with nutritional intake or supplementation.2
There were several limitations to this study. This study was a survey, with inherent biases associated with self-report rather than more direct food monitoring. Questions pertaining to the athlete’s motivation behind these dietary adherences (e.g., socio-cultural, weight management, performance benefits, etc.), as well as the duration and compliance surrounding these practices were not included in the survey. This study is the first to show the association between various dietary practices and ED/DE specifically in adolescent and young adult female athletes. A larger study of athletes with each of the specific dietary practices highlighted in this paper is needed to elucidate possible associations between such restrictive diets and the various health and performance-related consequences of RED-S.