Abstract
ncement of modern competitive sports, specialized training regimens and tai- lored dietary patterns collectively shape a distinctive gut microbiota in athletes. This unique ecosystem exhibits high microbial diversity and is enriched with beneficialbacteria—such as short-chain fatty acid-producing strains—that contribute to enhanced athletic perfor- mance, support energy homeostasis and neural coordination, and mitigate exercise-induced injuries, thereby improving competitive outcomes. This review elaborates on the char- acteristics of the athlete gut microbiome across different exercise modalities, examines how microbial changes may benefit or pose risks to athlete health, and provides a unique perspective for developing microbiota-driven personalized nutrition strategies aimed at optimizing athletic performance. Keywords:exercise; gut microbes; athletes’ diet; gut–brain axis 1. Introduction In recent decades, competitive global sports have shown a thriving trend, and athletes face an urgent demand to improve their performance. Among the numerous factors affect- ing athletic performance, training strategies, dietary patterns, and training environments have attracted much attention. Athletes need to obtain sufficient nutrition through a bal- anced diet and formulate appropriate training plans to maintain a good physical condition during high-intensity training and promote physical recovery after training. The gut microbiome is a complex ecosystem composed of approximately 100 trillion microorganisms. Its composition and functions
performance, training strategies, dietary patterns, and training environments have attracted much attention. Athletes need to obtain sufficient nutrition through a bal- anced diet and formulate appropriate training plans to maintain a good physical condition during high-intensity training and promote physical recovery after training. The gut microbiome is a complex ecosystem composed of approximately 100 trillion microorganisms. Its composition and functions are highly shapeable, and it is susceptible to the influence of various environmental factors such as medicine, age, and diet [1]. This dynamic characteristic makes it an ideal target for disease prevention and health interven- tion. Studies have shown that a variety of behavioral factors, including sleep patterns, circadian rhythms, physical activity, and dietary structure, can significantly regulate the composition and functions of the gut microbiota [2]. With the continuous advancement of high-throughput sequencing and culture-independent technologies, research has further clarified the core role of the gut microbiota in key physiological processes such as immune regulation, nutrient digestion, vitamin synthesis, and mood regulation [3]. The gut mi- crobiota can alleviate fatigue, enhance energy supply related to exercise endurance, and establish a major communication bridge with the brain, thereby driving the improvement of athletic performance. In addition, it can also help athletes achieve faster recovery and Life2025,15, 1812 https://doi.org/10.3390/life15121812
Life2025,15, 1812 2 of 21 enhance immune system function [4]. Significantly, due to their long-term high-intensity training and specific dietary patterns, elite athletes have developed a unique gut microbiota structure, which is believed to play a positive role in promoting their health status and athletic performance [5]. A thorough analysis of the formation mechanism and functional pathways of athletes’ gut microbiota and the pathways of function achievement can not only provide strong support for the precise formulation of athletes’ training programs and the scientific opti- mization of nutritional strategies, but also offer strategies for the general population to improve health and exercise capacity through microbiota intervention methods. Therefore, this review focuses on the shaping of athletes’ gut microbiota and explores the potential enhancing effects of the gut microbiota and its regulatory treatments on athletic perfor- mance. In-depth understanding and utilization of gut microbiota is expected to become a core component in the field of sports nutrition in the future. 2. Exercise-Driven Shifts in Gut Microbiota Composition Exercise, serving as a positive and effective lifestyle intervention, demonstrates a close and complex association with gut microbiota particularly in terms of microbial composition, metabolic functions, and other related fields. Numerous studies in humans and animals establish a bidirectional relationship between exercise and gut microbiota alterations. It is widely acknowledged that doing more exercise properly will increase the diversity of gut microbiota as well as the abundance of health-related bacteria [6]. Compared with less active individuals, athletes and people with long-term regular exercise routines exhibit considerable differences in gut microbiota composition. And multiple studies emphasize the positive impact of exercise on gut microbiota. In a study examining athletes across various sports categories, researchers selected 185 metagenomic samples from athletes with high anaerobic and aerobic training loads. The data illustrate significant differences in taxonomic composition and functional profiles of gut microbiota between athletes and sedentary populations. In microbial clusters represented by athletes, short-chain fatty acids (SCFAs)-producing bacteria demonstrate increased prevalence, notablyFaecalibacterium prausnitzii,Eubacterium rectale, andRuminococcus bromii[7]. In addition, a study by Kulecka et al. compared the exercise group with the control group by distinguishing different numbers
training loads. The data illustrate significant differences in taxonomic composition and functional profiles of gut microbiota between athletes and sedentary populations. In microbial clusters represented by athletes, short-chain fatty acids (SCFAs)-producing bacteria demonstrate increased prevalence, notablyFaecalibacterium prausnitzii,Eubacterium rectale, andRuminococcus bromii[7]. In addition, a study by Kulecka et al. compared the exercise group with the control group by distinguishing different numbers of taxa. The results showed that, compared with the healthy control group, the exercise group had a decreased abundance ofBacteroidesand an increased abundance of Prevotella[8]. These findings reveal the underlying association between the compositional charac- teristics of microbiota and specific exercise responses [9]. Sustained and regular exercise can serve as an effective strategy to optimize the gut microbial environment and enhance healthy status. In particular, for individuals with suboptimal baseline microbiota diver- sity or who lack stability, appropriate exercise can induce beneficial changes in microbial composition, thereby promoting overall health. 3. Exercise Characteristics Shape the Gut Microbiota of Athletes Population cohort-based studies have shown that the shaping of gut microbiota in athletes is associated with exercise. To be precise, the gut microbiota of athletes typically exhibits increased diversity and functional redundancy, and regular exercise is closely linked to beneficial gut microbiota structure. Research has demonstrated that a single bout of exercise can induce metabolic changes in athletes’ serum and feces, as well as trigger alterations in the gut microbiota, thereby exerting a series of effects on the overall physical health [10]. A study by Clarke et al. on rugby players further corroborated the beneficial effects of exercise. They found that the effects of exercise on the gut microbiota
Life2025,15, 1812 3 of 21 vary considerably depending on exercise types, intensity, and duration [11]. Next, we will detail certain elements that play a role in shaping the gut microbiota of athletes (Table). Table 1.Exercise-Related Gut Microbiota Characteristics. Type Influencing Factors Phenomena Conclusions Exercise patterns. Different Exercise Type Groupings - Moderate dynamic:Streptococcus ↑Anaerostipes hadrus↑ - High dynamic–low static: Bifidobacterium animalis↑ Enterococcus faecalis↑Lactobacillus acidophilus↑ - High dynamic–high static: Bacteroides caccae↑ The exercise mode determines the unique composition of the gut microbiota, and different exercise types shape the unique gut microbiota of athletes. Different Exercise Energy Metabolism and Metabolic Pathway Activation Microbiota replacement Exercise-induced microbiota diversity differences relate to energy metabolism and stress patterns. Different exercises activate distinct pathways, affecting gut microbiota. Differences in Specific Exercise Behaviors Endurance runners:α-diversity↑ Specific exercise behaviors may affect the characteristics of gut microbiota. Gender Dependency Male cyclists:Coriobacteriaceae↑, ifidobacterium↑, Pseudomonas↑ Female cyclists: Clostridiaceae↑, Lachnospiraceae↑, Ruminococcaceae ↑, Mitsuokella↑, Male runners: Catenibacterium↑ Female runners: Methanosphaera↑ Exercise-induced gut microbiota shaping shows gender differences related to metabolic homeostasis, sex hormone signals, and diet–microbiota interactions. Exercise Intensity Different Intensities of Exercise Training Moderate-intensity exercise: Prevotella↑ High-intensity exercise: Bacteroides↑,Butyricimonas↑, Odoribacter↑,Alistipes↑ Different exercise intensities lead to different gut microbial characteristics among participants. Different Training Frequencies for the Same Type of Exercise Cyclists with high training frequencies:Prevotella↑ Martial artists in the high-level group:Bacteroides↑ High-intensity exercise has a more positive impact on enhancing the diversity of gut microbiota. Vigorous and Prolonged Exercise Bifidobacterium↓,Ruminococcus↓, F. prausnitzii↓,Prevotella↑ Haemophilus↑,Mucispirillum↑, Ruminococcus gnavus↑ Excessive exercise has a negative impact on gut microbiota. Upward arrows indicate an increase and downward arrows indicate a decrease. 3.1. Exercise Patterns Among these factors, exercise type is the most significant one influencing the gut mi- crobiota of athletes. Different types of exercise induce variations in physical responses and energy metabolism, which in turn shape a unique intestinal environment. According to the body’s state during exercise and diverse patterns of muscle exertion, exercise can be divided into static and dynamic components. Results from LEfSe analysis of 37 international-level
responses and energy metabolism, which in turn shape a unique intestinal environment. According to the body’s state during exercise and diverse patterns of muscle exertion, exercise can be divided into static and dynamic components. Results from LEfSe analysis of 37 international-level
Life2025,15, 1812 4 of 21 athletes indicated the enriched bacterial species differed across sports category groups (SCG). For instance, in the moderate dynamic component group (e.g., fencing), bacteria such asStreptococcus suisexhibited a high correlation; specifically, the relative abundance of Anaerostipes hadruswas three times that of the other groups; in high dynamic–low static component group (e.g., hockey) was associated with species likeBifidobacterium animalis, the relative abundance ofFaecalibacterium prausnitziiandLactobacillus acidophiluswas 1.5 times and 25 times those of the other groups, respectively; in the high dynamic–high static component group (e.g., rowing), the group was linked toBacteroides caccae, whose relative abundance was 4.5 times that of the other groups [12]. This highlights that exercise patterns, rather than exercise itself, determine distinct gut microbiota compositions, and the type of exercise athletes engage in shapes their unique gut microbiota [5]. Previous studies have demonstrated that exercise-induced microbial diversity differences are closely related to the energy metabolic pathways and various physiological stress patterns across different sports (e.g., aerobic training vs. resistance training) [13,14]. For example, compared with resistance anaerobic exercise (RTE), a 2- week cardiorespiratory aerobic exercise (CRE) intervention reshaped the gut microbiota’s living environment by inducing changes in intestinal ischemia–hypoxia and permeability, leading to the replacement of low-abundance microbiota [15]. Non-targeted metabolomics studies have revealed that different exercise performances are associated with the activation of various metabolic pathways. This includes the urea and glutamine metabolism that may occur during exercise, which promotes the growth of urease-producingRomboutsia, Ruminococcus, andClostridium[10]. In addition, the upregulation of the butyrate synthesis pathway and changes in the abundance of metabolites such as lactate and ketone bodies also affect the interaction between the microbiota and the host, thereby altering the composition of the gut microbiota [16]. This kind of gut microbiota shaping may also be associated with specific exercise behaviors. For instance, during aerobic exercise, runners engage in dynamic movements such as jumping and landing; however, cyclists typically maintain a seated position and a fixed body posture. These differing exercise patterns probably contribute to the higher alpha diversity of the gut microbiota observed in endurance runners [17]. It is noticeable that the shaping
also be associated with specific exercise behaviors. For instance, during aerobic exercise, runners engage in dynamic movements such as jumping and landing; however, cyclists typically maintain a seated position and a fixed body posture. These differing exercise patterns probably contribute to the higher alpha diversity of the gut microbiota observed in endurance runners [17]. It is noticeable that the shaping effects of exercise on the gut microbiota exhibit a certain degree of gender dependence. Specifically, male cyclists show a relatively higher abun- dance ofBifidobacteriumandPseudomonas, as well as a significantly decreased abundance of Catenibacterium. In male runners, the abundances ofCatenibacteriumand methanosphaera are much higher [17,18]. For female athletes, however, female cyclists have notably higher abundances ofClostridiaceaeandRuminococcus, along with significantly lower abundances ofCoriobacteriaceaeandGemellaceae; in contrast, female runners show a considerably higher abundance of methanogens [17,19]. In fact, the sex-related differences in the gut microbiota of athletes are associated with multiple potential physiological mechanisms, including asymmetric metabolic homeostasis, sex hormone signaling, and gender-dependent diet– microbiota interactions [20,21]. On the one hand, when meeting the exercise requirements of the sport, due to physiological needs such as metabolic goals and hormonal regulation of nutrition [22,23], there are differences in dietary choices (type preferences, intake of nutritional supplements, and timing selection) between different genders. This difference may lead to gender-specific characteristics of the gut microbiota [24]. More importantly, sex steroid hormones (such as estrogen, progesterone, and testosterone) shape the gut microbiota through a bidirectional axis [25]. These differences directly regulate the host’s physiological environment, which in turn directionally affects the colonization and abun- dance of microorganisms [26].
Life2025,15, 1812 5 of 21 3.2. Exercise Intensity Exercise intensity is another key factor influencing gut microbiota. In a study in- volving a 4-week exercise program, participants were divided into a moderate-intensity group and a high-intensity group. The results showed that after 4 consecutive weeks of moderate-intensity exercise, the abundance ofPrevotellaincreased greatly; and in the high-intensity exercise group, the abundances ofBacteroides,Butyricimonas,Odoribacter, and Alistipesincreased significantly, while the abundances ofVeillonella,Dorea formicigenerans, andDorea longicatenaalso exhibited a volatile pattern [27]. A study focused on different intensity training conducted among 31 healthy college students indicated that participants in different groups showed distinctions in gut microbiota characteristics due to varying exercise intensities [28]. For the same type of exercise, different training frequencies may lead to the enrichment of specific gut microbiota. For example, among cyclists, those with a higher training frequency tend to have a higher abundance ofPrevotella[29]. Similarly, for martial arts athletes, those in the high-level group have a higher abundance ofParabac- teroidesandPhascolarctobacterium[30]. Overall, higher-intensity exercise exerts a more positive effect on enhancing the diversity of gut microbiota. However, the impact of exercise on the gut microbiota is not entirely positive [15]. Intense and prolonged exercise may raise the body’s inflammation level, impair intestinal barrier function, and thereby disrupt the balance of the gut microbiota [31–33]. Existing research has found that Improper, Irregular, and exhausting training Activity may be associated with certain changes in the gut microbiota [34]. For example, the numbers ofBifidobacterium,Ruminococcus, andFaecalibacterium prausnitziidecrease [35,36], while the proportion ofPrevotellaand bacteria related to the inflammatory process, such as Haemophilus,Roseburia,Mucispirillum, andRuminococcus gnavus, increase [37]. However, these associations are still in the stage of scientific exploration. There is an urgent need for further research in the future to identify microbial biomarkers that can accurately reflect gut bacterial imbalance caused by overtraining. For example, by combining multi-omics technologies with machine learning, we can uncover the changes in the gut microbiota and its metabolites, and search for more specific and sensitive microbial biomarkers. 4. Athletes’ Diets Deeply Participate in the Construction of the Gut Microbiota Ecosystem Beyond the training ground, the rigorous dietary regime of athletes also plays a
imbalance caused by overtraining. For example, by combining multi-omics technologies with machine learning, we can uncover the changes in the gut microbiota and its metabolites, and search for more specific and sensitive microbial biomarkers. 4. Athletes’ Diets Deeply Participate in the Construction of the Gut Microbiota Ecosystem Beyond the training ground, the rigorous dietary regime of athletes also plays a pro- found role in shaping the gut microbiota ecosystem. Relevant studies have revealed that dietary changes can account for 57% of the total structural variation in the gut micro- biota [38]. To maximize athletic performance, elite athletes typically adhere to strict training and dietary plans. Owing to the requirements of high-intensity training and competitions, athletes typically experience an increase in their total energy and nutrient intake. Moreover, they consume larger amounts of protein and carbohydrates according to the specific type of sport they participate in [39,40]. The unique athletic diet is deeply involved in the con- struction and regulation of the gut microbiota ecosystem, exerting a fundamental influence. Athletes’ dietary intake provides direct metabolic substrates for microorganisms; different dietary combinations can rapidly induce changes in the composition and functional output of the microbiota, and may even play a synergistic or antagonistic regulatory role in the interaction between exercise and the microbiota [41]. 4.1. High-Carbohydrate Diet High carbohydrate intake is generally considered to be highly associated with athletic performance [42–44]. The High-Carbohydrate Diet (HCD) has been widely proven to significantly improve endurance performance, thus becoming the preferred dietary strategy
Life2025,15, 1812 6 of 21 for athletes engaged in high-intensity endurance sports. A dietary intervention study indicated that during HCD intervention, the proportions ofLeuconostoc,Lactococcus, and Collinsellaincreased, while the relative abundance ofStreptococcusdecreased after HCD intervention [45]. In addition, lactose, as a common high-sugar nutritional supplement, has recently been shown to possess prebiotic properties; it can effectively enrich the abundance ofBifidobacteriumandLactobacillusby regulating the gut microbiota [11]. On the other hand, dietary fiber, as an important component of carbohydrates, de- serves our attention. Excessive dietary fiber intake can cause digestive system sensitivity and increase the frequency of defecation in competitive athletes, thereby reducing train- ing effectiveness. However, a long-term diet lacking dietary fiber can decrease microbial diversity and impair the health of athletes’ gut microbiota [12]. Increasing dietary fiber intake can regulate the intestinal microenvironment, inhibit the proliferation of harmful bacteria, which contribute to the improvement of athletes’ microbial diversity [7]. Results from animal experiments have manifested that dietary fiber supplementation can regulate the gut microbiota of mice undergoing overtraining and enhance certain aspects of exercise performance [29]. Additionally, after increasing dietary fiber intake, there is an association with elevated proportions ofPrevotella,Bacteroides, andBifidobacteriumspecies, as well as greater gut microbiota stability [46]. Furthermore, it helps upregulate the expression of fiber-modulated microbial metabolic pathways, such as glycan metabolism—genes encoding carbohydrate-active enzymes exhibit activity toward fibers or host glycans. Although a high-carbohydrate diet is foundational for athletic performance, emerging evidence highlights potential risks associated with its long-term implementation, neces- sitating a more nuanced approach. Certain athletes may exhibit transient blood glucose fluctuations resembling pre-diabetic states following chronic high-carbohydrate intake [47]. Animal studies further suggest that specific types of carbohydrates, particularly simple sugars, can exacerbate inflammatory responses and contribute to metabolic disorders un- der certain conditions [48,49]. Additionally, excessive carbohydrate intake, especially of refined sources, may enrich potentially detrimental bacterial taxa such asEnterococcusand Klebsiella pneumoniae[50,51], potentially predisposing athletes to intestinal and systemic inflammation [52]. It is also important to note that dietary fiber supplementation, while generally beneficial, may cause gastrointestinal distress (e.g., bloating, flatulence) in indi- viduals with specific gut microbiota deficiencies [53,54]. Therefore, carbohydrate and fiber
Additionally, excessive carbohydrate intake, especially of refined sources, may enrich potentially detrimental bacterial taxa such asEnterococcusand Klebsiella pneumoniae[50,51], potentially predisposing athletes to intestinal and systemic inflammation [52]. It is also important to note that dietary fiber supplementation, while generally beneficial, may cause gastrointestinal distress (e.g., bloating, flatulence) in indi- viduals with specific gut microbiota deficiencies [53,54]. Therefore, carbohydrate and fiber recommendations must be individualized, considering the athlete’s unique physiological status, microbial baseline, and the specific type of carbohydrates consumed. 4.2. High-Protein Diet Compared with the traditional high-carbohydrate diet, the High-Protein Diet (HPD) is also popular among athletes. From a nutritional perspective, protein is rich in a variety of essential amino acids, which are of vital significance for maintaining muscle mass and improving athletic performance [55,56]. Meanwhile, the intake of meat in the diet is often related to the composition of intestinal bacterial groups. A study on endurance athletes con- ducted by Diego et al. showed that after protein supplementation, the relative abundance of the phylumSynergistetes, the orderSynergistales, and the classSynergistiadeclined greatly. Among them, the familyLachnospiraceaehad the most significant decrease, followed by the generaRoseburia,Blautia, andCoprococcus. A further comparison between the protein supplementation group (PRO group) and the control group after 10 weeks of intervention revealed that the PRO group displayed the following microbial features: enhanced relative abundance of the phylumBacteroidetes, reduced relative abundance of the phylumFirmi- cutes, a prominent increase in the genusBacteroidesproportion, and a significant decline in the proportions of the generaCitrobacterandKlebsiella[57]. Another study that focuses
Description
This review explores how exercise and diet influence athletes' gut microbiota.