Dietary Intake, Body Composition and Performance of Professional Football Athletes in Slovenia

is the rst study to examine the nutritional status of professional Slovenian football players. This study aimed to analyze the dietary intake of elite football players during their prepa- ration phase of the season and to investigate whether there is a relationship between energy and macronutrient intake with body composition and physical performance. Twenty-three footballers completed a three-day dietary and physical activity diary and underwent body composition mea- surements via bioelectrical impedance vector analysis (BIVA). Fifteen participants also took part in the Cooper treadmill test to assess their physical performance in correlation with their nutritional intake. Football players had an energy intake that was signi cantly too low for their needs, re ecting low energy availability. The average carbohydrate (CHO) intake was below the Union of European Football Associations (UEFA) recommendations, i.e., <4 g CHO/kg body weight (BW). Additionally, players had adequate intakes of protein and fat, and inadequate intakes of saturated fat, ber, calcium and vitamin D. There was a positive correlation between protein intake and lean body mass. Addi- tionally, a negative correlation was observed between body fat mass and carbohydrate intake as well as between performance with the percentage of energy intake from fat. Results

Additionally, players had adequate intakes of protein and fat, and inadequate intakes of saturated fat, ber, calcium and vitamin D. There was a positive correlation between protein intake and lean body mass. Addi- tionally, a negative correlation was observed between body fat mass and carbohydrate intake as well as between performance with the percentage of energy intake from fat. Results of this study highlight what aspects of nutrition might be improved upon in professional football players to maximize performance, longevity and body composition of athletes, as well as the necessity of a nutritionist role in this process. Keywords: low energy availability; relative energy de ciency in sport; energy imbalance; sports performance; body composition measurement 1. Introduction Football is currently one of the most popular sports in the world, and it places high demands on athletes' physical capacity [1–3]. Professional soccer players must possess several sports related skills such as speed, endurance, mobility, exibility, ball handling skillfulness and rapid decision-making during training and competition. In addition, the physiological demands of this sport are based on medium- to long-distance running coupled with short high-intensity movement blocks with variable patterns and shorter rest periods [3–5]. Football players use both anaerobic and aerobic systems during training and matches and possess unique energy and nutrient needs depending on the nature and periods of training and competition [1,6]. As such, nutrition plays an important role in optimizing performance and maintaining overall health and training longevity throughout the season. Nutrition can either potentiate or attenuate exercise-induced adaptations [7,8]. A balanced diet plays a key role in proper recovery and optimal sports performance. Changes in food intake in response to certain periods of training are also of great importance within the so-called periodization of nutrition paradigm [6,9]. Properly periodized nutrition supports performance and energy levels throughout the competition season and/or training Nutrients2023,15, 82.

Nutrients2023,15, 82 2 of 25 period [7,9,10]. Nutritional requirement can usually be met with a balanced diet combined with evidence-based supplementation. Detailed guidelines on nutritional needs of elite football players can be found in the UEFA expert group statement on nutrition in elite football [7]. Despite the increased interest in nutrition and the use of nutritional supplements to improve performance, some athletes still consume a sub-optimal diet even at the elite level [11–14]. Thus, the purpose of this article was to: Evaluate the nutritional intake (energy, macronutrient and micronutrient intake) of professional football players of a football club playing in the First Slovenian League. Investigate possible correlations between dietary intake and body composition. Explore possible correlations between nutritional intake and physical performance. Present the importance of a nutritional consultant and the monitoring of nutritional intake as a method for optimizing the performance of football players and preventing relative energy de ciency syndrome (RED-S). Based on this the following hypotheses were determined: Hypothesis 1: Football players consuming the recommended amount of protein (1.6–2.2 g/kg BW) and carbohydrates (4–8 g/kg BW) will have a body composition with a higher percentage of lean BW. Hypothesis 2: Football players who consume the recommended amount of protein (1.6–2.2 g/kg BW) and carbohydrates (4–8 g/kg BW) will cover a longer distance in the Cooper performance test. Hypothesis 3: Football players with an energy availability 30 kcal/kg fat free mass (FFM) will cover a longer distance in the Cooper test. This article provides insights into the nutritional needs and dietary habits among Slovenian professional football players, their energy, macro- and micro-nutrient intakes as well as dietary supplementation habits. The results of this study offer unique insights for football players, nutritionists within the team, coaches, parents of younger players and medical staff on optimizing the performance and recovery of football players and, most importantly, protecting the long-term health of these professional athletes. 2. Materials and Methods Work methods included a review of the current literature, assessment of food diaries using the Prodi program (PRODI ® 6.4 Expert program, Stuttgart, Deutschland), assessment of body composition and a physical tness

players and medical staff on optimizing the performance and recovery of football players and, most importantly, protecting the long-term health of these professional athletes. 2. Materials and Methods Work methods included a review of the current literature, assessment of food diaries using the Prodi program (PRODI ® 6.4 Expert program, Stuttgart, Deutschland), assessment of body composition and a physical tness test using the Cooper test. Results were statisti- cally analyzed using the appropriate statistical method and the results regarding nutritional intake were compared to the UEFA recommendations. Ethical approval was given by the Medical Ethics Commission of the Republic of Slovenia (protocol code 0120-245/2022/3, 25 July 2022). Subjects participated in the study voluntarily and could withdraw from the study at any point. 2.1. Subjects 25 football players aged between 18 and 35 were invited to participate in this study. All football players were members of the same club that plays in the First League of Slovenian football. Twenty-three professional football players aged between 18 and 31 responded to the invitation. This sample was chosen as we expected it to be quite homogeneous, as the footballers had a similar height and weight, level of physical tness, training regimen as well as consuming two similar meals at the football club. The latter is a requirement of the football club were subject trained and competed at and the meals are prepared by the club's chef. 2.2. Nutritional Assessment The dietary intake of football players was assessed using 3-day food diaries (Appendix ). Diaries were provided with detailed instructions and an example of how to log in food to

Nutrients2023,15, 82 3 of 25 avoid incorrect or inaccurate logging. Subjects were asked to provide as detailed descrip- tions as possible of the foods and liquids consumed as well as any nutritional supplements used. Subjects were asked to pay special attention to assembled dishes at home or in restau- rants (e.g., risottos, meat platters, soups) and to photograph them if possible. Additionally, subjects they were also given researchers contact information and an initiative to contact the research team if there were any questions regarding the process and food logging. Three-day food diaries were used for nutritional assessment where participants reported their eating habits on two days during the week and one day during the weekend. After completing the food diaries, each subject sat down with one of the researchers to revise the completed diaries. 2.3. Physical Activity Evaluation In addition to the food diaries participants were also instructed to ll out a physical activity diary for three days (Appendix), in which they collected all physical activities performed during the recording of the food diaries—that is, two days during the week and one day during the weekend. Here, too participants we asked for detailed recording regard- ing the type of exercise they performed as well as the intensity and duration of exercise. As subjects were part of the same club their activities in training were mostly matched. Based on these data, we calculated the metabolic equivalent (MET) value using data for individual activities from Ainsworth et al. [15]. Exercise energy expenditure (EEE) was then calculated by summation of energy expenditure of all activities. Based on these data, energy availability was calculated from energy intake analyzed through food diaries, EEE reported by football players in their physical activity diary and FFM obtained by body composition measurement using the equation by Loucks et al. [16]: Energy availability= energy intake(kcal) EEE(kcal) FFM(kg) 2.4. Body Composition Assessment Body mass index (BMI) and height of the subjects were measured using a scale with a stadiometer. Based on this, we calculated BMI. Body composition measurements such as FFM and fat mass (FM) were obtained using BIVA (BIA

by body composition measurement using the equation by Loucks et al. [16]: Energy availability= energy intake(kcal) EEE(kcal) FFM(kg) 2.4. Body Composition Assessment Body mass index (BMI) and height of the subjects were measured using a scale with a stadiometer. Based on this, we calculated BMI. Body composition measurements such as FFM and fat mass (FM) were obtained using BIVA (BIA 101 BIVA ® PRO, Class IIa Medical Device—93/42/EEC Class IIa Medical Device—93/42/EEC, Akern, Pisa, Italy), which does not provide segmental analysis and uses a three-compartment model, dividing the body into Body Cell Mass (BCM), Extra Cellular uids and solids (ECM) and FM, where FFM = BCM + ECM. 2.5. Performance Assessment Sports performance of participants was tested using the Cooper test. [17] The max- imum distance participants could cover in 12 min was measured. Among 23 football players, 15 performed this test. A treadmill was used to ensure that conditions were as similar as possible for all subjects in terms of heath, wind and other weather conditions. Football players arrived at the testing site about an hour before the start to properly warm up and prepare before the test. The pace of each run was dictated but not disclosed to the individual by each subject himself, with the goal of covering the longest distance possible as done in previous research [18]. After completing the test participants could continue running at a lower intensity for a while to cool down. A quali ed professional as well as doctor was also present throughout the testing, so that the process was carried out safely under expert guidance and in a safe environment. 2.6. Statistical Analysis All data obtained from food diaries, body composition measurements and perfor- mance test were statistically analyzed using Excel 2016 (Microsoft Of ce, Redmond, WA, USA) and the statistical analysis programming language R (R version 4.1.0). Descriptive

Nutrients2023,15, 82 4 of 25 statistics were determined: minimum (min) and maximum (max) value, mean value (x) and standard deviation (SD). Additionally, non-parametric tests: Wilcoxon rank sum test (two-tailed test) and Welch'sttest (for two independent samples) were also used when ap- plicable. To compare macronutrients intake with the UEFA recommendations a one-sided t-test was used to compare whether the sample averages differed from the recommenda- tions. The normality of the distribution of individual variables and the equality of variances for independent samples were checked with the Shapiro–Wilk test. Pearson's correlation coef cient (r) was used to examine correlations between the selected variables. Statistically signi cant differences between the studied groups or association between variables were con rmed if thep-value was less than 0.05. 3. Results 3.1. Sample Characteristics The sample size included 23 professional football players. The average age of the subjects was 24 years, with the youngest participant aged 18 and the oldest 31. On average, they were 182 cm tall, weighed 78 kg and had an average BMI of 23.4 kg/m 2 . They had different percentages of FFM, ranging from 66 to 86%. They also had a large range in fat mass (from 13.9 to 31%). Through recorded daily physical activity (Appendix), we calculated MET for each player and obtained an average value of 12.8 MET/day. Their mean EEE was 982 kcal, with a large range of 54 to 1309 kcal/day. On recorded days participants were variously active, some had rest days, while others lled in the diary during intensive multi-day training sessions. The basic characteristics of the sample are presented in Table. Table 1.Participant characteristics. Variable Mean SD Range Age (year) 24 3.4 19–31 Height (cm) 182 6.2 169–192 Body mass (kg) 78 7.4 60.5–88 BMI (kg/m 2 ) 23.4 1.2 20.5–25.2 FFM (kg) 59.4 4.8 49.4–66.7 FFM (%) 76.4 4.1 66.3–86.1 FM (kg) 18.2 3.8 8.7–24.8 MET 23.1 3.5 13.9–31.0 EEE (kcal) 12.8 4.5 0.6–15.1 SD—standard deviation; BMI—body mass index; FFM—fat free mass; FM—fat mass; MET—metabolic equivalent of activity; EEE—exercise energy expenditure. 3.2. Dietary Intake Evaluation Dietary habits of football players were assessed using 3-day

(kg/m 2 ) 23.4 1.2 20.5–25.2 FFM (kg) 59.4 4.8 49.4–66.7 FFM (%) 76.4 4.1 66.3–86.1 FM (kg) 18.2 3.8 8.7–24.8 MET 23.1 3.5 13.9–31.0 EEE (kcal) 12.8 4.5 0.6–15.1 SD—standard deviation; BMI—body mass index; FFM—fat free mass; FM—fat mass; MET—metabolic equivalent of activity; EEE—exercise energy expenditure. 3.2. Dietary Intake Evaluation Dietary habits of football players were assessed using 3-day weighted food diaries. Data were then analyzed using the PRODI ® 6.4 Expert program and R statistical processing programming language (R version 4.1.0, Vienna, Austria). Energy availability was calcu- lated using the formula by Loucks et al. [16] as explained in greater detail in the methods section. The average values of energy intake and energy availability, as well as the intake of carbohydrates, proteins, fats, saturated fats and bers are presented in Table. 3.2.1. Energy Availability The normality of data distribution was tested using the Shapiro–Wilk test, which con rmed normal distribution of energy availability data (p> 0.05). The average energy intake was 2700 kcal and in the majority of subjects energy intake changed proportionally with a higher or lower EEE on a given day. Energy availability was calculated [9] because it gives further insights on energy balance than energy intake, as it takes into account energy intake, EEE and FFM. Values below 30 kcal/kg FFM as clinically low energy availability, values between 30 and 40 kcal/kg FFM as subclinical low energy availability, and optimal or high energy

Nutrients2023,15, 82 5 of 25 availability as equal to or exceeding 40 kcal /kg FFM [19,20]. For women, this limit was set slightly higher, above 45 kcal/kg FFM [19]. Using a one-sidedt-test, we found that the sample average of energy availability is statistically signi cantly lower than 40 kcal/kg FFM (t= 6.23, df = 22,p< 0.001). The average energy availability of the subjects was 29 kcal/kg FFM, which corresponds to the criteria of clinical energy availability (Figure).Nutrients 2023, 15, 82 6 of 27 Figure 1. Energy availability among football players. Dots represent individual participants (n = 23). The red line indicates the upper limit of clinical energy availability (30 kcal/kg FFM) and the green line the lower limit of optimal energy availability (40 kcal/kg FFM). 3.2.2. Macronutrient Intake The Shapiro–Wilk test indicated normal distribution of data (p > 0.05) for carbohy‐ drate, protein and fat intake. During the recording of food and physical activity diaries, the football players were in preseason training period. For this period, a carbohydrate intake between 4 and 8 g CHO/kg BW is recommended. The average carbohydrate intake among soccer players was 3.6 g/kg BW. A one‐tailed t‐test showed that the sample mean carbohydrate intake is statistically significantly lower than 4 g/kg BW (t = −2.25, df = 22, p = 0.017). Most football players did not reach the lower recommended UEFA lower limit of 4 g CHO/kg body weight for preseason training (Figure 2). Figure 1. Energy availability among football players. Dots represent individual participants (n= 23). The red line indicates the upper limit of clinical energy availability (30 kcal/kg FFM) and the green line the lower limit of optimal energy availability (40 kcal/kg FFM). 3.2.2. Macronutrient Intake The Shapiro–Wilk test indicated normal distribution of data (p> 0.05) for carbohydrate, protein and fat intake. During the recording of food and physical activity diaries, the football players were in preseason training period. For this period, a carbohydrate intake between 4 and 8 g CHO/kg BW is recommended. The average carbohydrate intake among soccer players was 3.6 g/kg BW. A one-tailedt-test showed that the sample mean carbohydrate

data (p> 0.05) for carbohydrate, protein and fat intake. During the recording of food and physical activity diaries, the football players were in preseason training period. For this period, a carbohydrate intake between 4 and 8 g CHO/kg BW is recommended. The average carbohydrate intake among soccer players was 3.6 g/kg BW. A one-tailedt-test showed that the sample mean carbohydrate intake is statistically signi cantly lower than 4 g/kg BW (t= 2.25, df = 22, p= 0.017). Most football players did not reach the lower recommended UEFA lower limit of 4 g CHO/kg body weight for preseason training (Figure).

Nutrients2023,15, 82 6 of 25Nutrients 2023, 15, 82 7 of 27 Figure 2. Carbohydrate intake among football players. Dots represent individual participants (n = 23). The red line indicates the lower limit of the recommended intake for football players in the preseason period (4 g/kg BW), and the green line indicates the upper limit of the recommendation (8 g/kg BW). Dietary intake of protein and fat was adequate among subjects. On average, they con‐ sumed 1.8 g of protein/kg BW, which is in line with the recommendations (1.6–2.2 g pro‐ tein/kg BW). However, 35% of football players did not reach the lower limit of 1.6 g of pro‐ tein/kg body weight (Figure 3). The range of protein consumption among football players was between 0.9 to 3.5 g/kg BW. A one‐tailed t‐test showed that the sample mean protein intake is not statistically significantly higher than 2.2 g/kg BW (t = −3.46, df = 22, p = 0.99). Figure 2. Carbohydrate intake among football players. Dots represent individual participants (n= 23). The red line indicates the lower limit of the recommended intake for football players in the preseason period (4 g/kg BW), and the green line indicates the upper limit of the recommendation (8 g/kg BW). Dietary intake of protein and fat was adequate among subjects. On average, they consumed 1.8 g of protein/kg BW, which is in line with the recommendations (1.6–2.2 g protein/kg BW). However, 35% of football players did not reach the lower limit of 1.6 g of protein/kg body weight (Figure). The range of protein consumption among football players was between 0.9 to 3.5 g/kg BW. A one-tailedt-test showed that the sample mean protein intake is not statistically signi cantly higher than 2.2 g/kg BW (t= 3.46, df = 22, p= 0.99). The percentage of fat intake varied greatly between players—from 24% to 45% of their total daily energy intake. The recommendation for fat intake is up to 35% of the daily energy intake, and the average percentage of fat intake among the subjects was 34.7%, i.e., just below the upper limit of the recommendations (Figure). Since fat

= 22, p= 0.99). The percentage of fat intake varied greatly between players—from 24% to 45% of their total daily energy intake. The recommendation for fat intake is up to 35% of the daily energy intake, and the average percentage of fat intake among the subjects was 34.7%, i.e., just below the upper limit of the recommendations (Figure). Since fat intake is restricted only by the upper limit and every fat intake below that limit is considered in line with UEFA recommendations, we investigated only if our sample's fat intake is higher than the recommended percentage of fat intake. Due to the inherent directionality of our investigation, we used a one-sidedt-test, which showed that the sample average of the percentage of fat in the diet is not statistically signi cantly higher than 35% of the total energy intake (t= 0.29, df = 22,p= 0.62).

The study evaluates dietary intake and its impact on body composition and performance in Slovenian football players.