Our study sought to identify sex-related differences in dieting patterns in a group of endurance athletes. This is the first study, to our knowledge, to fully encompass the persistent sex-related differences in planned dietary patterns, providing evidence toward the influence of diet culture in female endurance athletes. The major findings of our study were: 1) female endurance athletes were more likely to have attempted and discontinued a planned diet strategy previously and have a greater number of total diet attempts; 2) female endurance athletes were more likely to follow carbohydrate and energy restricted diets, plant-based diets, and elimination diets (ex: gluten/dairy-free); and 3) female endurance athletes were more likely to follow, currently or previously, a planned diet for personal reasons compared to males who’s motivation appeared more performance oriented.
Manipulation of one’s body mass is a common component of many endurance sporting events. For instance, competitive cyclists may attempt to lose weight leading up to competition to improve power-to-weight ratio. [15] Marathon runners may also desire a lower body mass to increase running speed during competition. [16] Although body weight alterations are common in endurance sports, less is known about the dieting strategies endurance athletes employ to achieve an ideal body composition, weight, or both. While these strategies appear advantageous and often result in initial success, continual efforts to replicate a specific body composition or performance outcome may lead to DE behaviors. [3, 7] However, determining whether an endurance athlete has an increased risk for DE is difficult due to the dieting culture integrated into endurance sports, specifically for female athletes. Professional organizations suggest that unhealthy and persistent dietary behaviors represent an increased risk for eating disorders. [17] Thus, quantifying dieting frequency may be an initial indicator of DE behaviors in endurance athletes.
Notably, our study objectively measured dieting frequency and history, showing that ~ 30% of endurance athletes were currently following a planned diet and of those not currently following a planned diet, 55.6% had attempted to follow at least one diet previously. While there are few studies [13, 14] that report dieting frequency or history in a sample of heterogenous endurance athletes, the combined frequency observed in our study is similar to that reported in elite Olympic weight-class athletes. [18] Specifically, our study showed that female endurance athletes were more likely to attempt and discontinue a planned dietary strategy, more likely to have attempted ≥ three different dietary strategies, and had a significantly greater number of planned diet attempts compared to male endurance athletes. The extensive dieting frequency in female endurance athletes supports the persistent component of DE evidenced by studies in athletes showing associations between dieting and eating behaviors. [19] Thus, collecting diet frequency prior to programming may assist coaches and sports dietitians in early detection of DE for female endurance athletes.
Shifts in sports nutrition have recently focused on personalized dietary prescription. [20] However, appropriately individualized dietary prescriptions are often only available to those with access to nutrition professionals. Those without access to nutrition professionals, such as the recreational endurance athletes in our study, are more reliant on coaches and media for diet prescription. [21] As a result, popular diets that receive considerable media attention are commonly employed. This may be problematic given that endurance athletes require greater energy intake, but most popular diets promote severe restriction of at least one macronutrient, total energy, and/or entire food items or categories. Though, the extent to which endurance athletes follow these diets has been underexplored.
The findings from our study show that female endurance athletes are more likely to follow carbohydrate restriction diets. A common reason for carbohydrate restriction in athletes is to increase the body’s ability to use fat as the primary energy source at exercise intensities where it would normally use glycogen. The transition from carbohydrate to fat utilization at higher exercise intensities promotes glycogen sparing and improved makers of aerobic performance; however, this has not shown to improve competition outcomes. [22] Although there is theoretical rationale for employing carbohydrate restriction in endurance sports, the prevalence of previous carbohydrate restriction in our group of female athletes is likely because female athletes in our study were predominately runners. As previously discussed, thinner figure is often more desirable for runners. [8] Female runners may also be more concerned that a larger proportion of carbohydrates in their diet could lead to increases in fat mass. The degree of carbohydrate intake proposed for endurance athletes may also cause hesitation due to anticipation of future weight gain. Irrespective of sport, females tend to report a greater concern for carbohydrate intake compared to males [23] which was supported by our adjusted analyses. Regardless, severe carbohydrate restriction may be attractive to female endurance athletes given the diet’s ability to produce rapid weight loss. However, there are many concerns with persistent carbohydrate restriction. Several studies report the appetite suppressive effects of carbohydrate restriction diets. [24] Because endurance athletes require sufficient energy to support their training, diets that reduce appetite in conjunction with decreased energy intake from acute exercise-induced anorexia may lead to LEA [25]. Other concerns with low-carbohydrate diets include the rapid reduction in markers of bone health, [26] hypercholesterolemia, [27] and nutrient deficiencies. [20]
Carbohydrate restriction often coincides with general energy restriction given that the near-complete removal of carbohydrates is difficult to replace. This is supported by our finding that female athletes showed more persistent attempts at both carbohydrate and energy restriction diets. Energy restriction diets were higher in female athletes and female athletes had a lower BMI than male athletes. The emphasis on energy restriction despite lower BMI may indicate DE behaviors that are coupled with (or originate from) a hyper fixation on achieving a sport-specific body type. [6] Given the high energy requirements necessary to support endurance exercise and that female athletes habitually consume less energy than they expend, [28] it is difficult to recommend continual energy restriction to female endurance athletes. Sufficient energy intake is critical in bone mineral formation, reproductive health [29], and limiting common nutrient deficiencies observed in female athletes. [24] Moreover, Coelho et al. [7] suggests that athletes at the highest risk for eating disorders are those who restrict energy intake.
Coelho et al. [7] also suggests that vegetarian athletes are amongst those with a higher risk for the development of eating disorders. In our study, it was more common for female athletes to follow plant-based diets compared to male athletes. This trend was observed in females currently on a planned diet and those with previous diet attempts and was similar to what has been reported in elite athletes [30]. Interestingly, female athletes were more likely to follow a plant-based diet for personal reasons. Given that most athletes currently following a planned diet reported continuous implementation of their strategy, it is possible that social/cultural (animal-activism, agricultural concerns, cultural and/or religious restriction, etc.) influences made up a considerable number of these personal reasons. Orthorexia nervosa, characterized as an obsession with healthy eating that is associated with restrictive behaviors, [31] may be another reason female athletes are more likely to follow a plant-based diet. In other words, because dietary restrictions are common in orthorexia nervosa as a result of this obsession, there could be a crossover between orthorexia nervosa (restricting dietary intakes to only “healthy” foods) and plant-based diets (restricting dietary intakes to only “plant-based” food which are often considered to be “healthy”). While orthorexia nervosa may not be initially associated with sport-specific DE, excessive exercise combined with an obsession to restrict “unhealthy” foods certainly corresponds with DE behaviors. Interestingly, male athletes were more likely to follow a balanced diet suggesting that they did not share a similar obsession with the removal of specific foods or rigid surveillance. On the other hand, in those not currently following a planned diet, the attempt and rapid discontinuation of a plant-based diet refutes the aforementioned motivations (personal reasons, orthorexia nervosa, etc.) and thus, are likely more aligned with achieving an ideal figure. Similar to low-carbohydrate strategies, plant-based diets have several benefits for endurance athletes. For instance, plant-based diets have shown to increase muscle glycogen stores, delay fatigue, and reduce inflammation and oxidative stress when energy intake is sufficient. [20] However, similar to other restrictive diets, athletes following vegetarian diets are at a higher risk for micronutrient decencies and LEA. [32]
Although we were unable to conduct an inferential analysis, female endurance athletes were more likely to attempt either a diary- or gluten-free diet. Endurance runners frequently experience exercised-induced gastrointestinal symptoms and often avoid particular foods. [33] The elimination of dairy and gluten from diet may be a common approach for endurance athletes to alleviate gastrointestinal issues with or without a known intolerance. However, reports show no sex-related differences in the frequency of gastrointestinal symptoms following endurance exercise. [34] If the reasons for employing dairy- and gluten-free diets were solely associated with gastrointestinal issues, the proportion would theoretically be more balanced between sexes. Thus, it is plausible to consider that the motivation to follow dairy- and/or gluten-free diets likely aligns more with orthorexia nervosa than gastrointestinal health for female athletes. In fact, the primary risks of employing a dairy- or gluten-free diet align with LEA and micronutrient and fiber deficiencies [32]. However, it is unknown if these diets alone result in chronic LEA.
Our data suggest that female endurance athletes are subjected to the diet culture of endurance sports to a greater degree than their male counterparts by way of increased dieting frequency and diet selection and may be at a greater risk for developing eating disorders associated with endurance sports thus supporting our hypothesis. Despite the risks associated with many popular diets, it is certainly possible to employ them effectively if closely monitored. However, most attempted diets appeared to create considerable burden and the majority were abandoned within three months. While it is unclear exactly what contributes to such unsuccessful diet attempts in endurance athletes, the restrictive nature of popular diets may be too difficult for long-term implementation. However, despite the reported obstacles, we still observed a high dieting frequency and an openness to future diet attempts. Thus, the implementation of frequent and restrictive diets is likely to remain and coaches and sports dietitians should prioritize screening and surveillance during programming and prioritizing fueling for training.
The current study had several limitations that warrant discussion. First, our study was based on self-report which may lead to inaccuracies in reporting, especially considering that the questionnaire was non-validated. Additionally, the cross-sectional nature of the study may have resulted in dietary practices that differ from general intakes given that practices vary by training/competition cycles. However, our study was conducted across a nine-month period which may have accounted for differences by season although this was not included in the analysis. Future studies should determine the dieting patterns of endurance athletes across timepoints within an athletic season. The study period also took place during the COVID-19 pandemic and responses may not have been indicative of habitual intake. However, it is unlikely that COVID-19 significantly influenced total dietary history. Our sample also had uneven proportions of professional, collegiate, and amateur endurance athletes. However, our sample was mostly amateur athletes, followed by collegiate, and professional and likely similar to the true prevalence of endurance athletes. Our study also did not ask for subcategories of many branded diets (i.e., adapted ketogenic diet, ovo-vegetarian, etc.) which may have revealed other dietary patterns. However, athletes were instructed to report and describe diet combinations, diet sub-categories, and diets that were not listed as “other”. Our study did not ask about dieting history in those currently following a planned diet. However, our results indicate that the majority of these endurance athletes sustained their practice for at least one year.