Association of Low Energy Availability and Suppressed Metabolic Status in Korean Male Collegiate Soccer Players: A Pilot Study

Prevalence of low energy availability and associations with seasonal changes in salivary hormones and IgA in elite male Gaelic footballers

PURPOSE

Evidence suggests low energy availability (LEA) is prevalent in elite male Gaelic football (GF) players. Previous research in male and female team sports found LEA may negatively impact endocrine function. The aim of this study was to examine the seasonal variations in energy availability (EA) and its associations with salivary measures in elite male GF players across the competitive season.

METHODS

Energy availability was assessed using field-based methods in conjunction with salivary testosterone (s-T), cortisol (s-C) and immunoglobin A (s-IgA) concentrations at pre-season (PRE), in-season (IN) and post-season (POST).

RESULTS

38% reported LEA at PRE, 33% at IN, and 28.5% at POST. s-C, s-T and s-IgA levels were within normal ranges at PRE, IN and POST. Salivary cortisol declined significantly from PRE to IN, remaining reduced at POST. Salivary testosterone decreased significantly from PRE to IN but was significantly elevated at POST compared to IN. Salivary IgA was significantly greater at POST than IN. No significant associations were found between s-C or s-T and EA at any time point. Pre-season s-IgA exhibited a significant inverse association with PRE EA. Decreased s-IgA flow rate and s-IgA secretion rate were significantly associated with decreased EA at PRE. Reduced carbohydrate (CHO) intake was also associated with decreased s-IgA secretion rate at PRE.

CONCLUSION

This study suggests that LEA is prevalent in elite male GF players, but is not associated with s-C or s-T. However, EA is associated with s-IgA which may impact the immune system. Therefore, education and interventions surrounding the prevalence and associations of EA should be implemented in this population.

Energy availability and macronutrient intake in elite male Gaelic football players

Evidence suggests that Gaelic football (GF) players do not meet the recommended energy intake (EI) levels and therefore may be at risk of low energy availability (LEA). This study examined energy availability (EA) in 20 elite male GF players. At two stages during a season (2019-2020), repeated measures of EI, exercise energy expenditure (EEE), EA and body composition were performed. Sixty-five percent reported with LEA [<30 kcal.kg Lean Body Mass (LBM)^-1.day^-1] at pre-season (PRE), with 70% at in-season (IN). Mean daily carbohydrate intake (PRE 3.2 ± 0.82 g.kg; IN 3.4 ± 0.79 g.kg) was below the recommended intake (5-7 g.kg) in 95% at PRE and 100% at IN. All consumed the recommended daily amount of protein (PRE 1.85 ± 0.57 g.kg; IN 1.87 ± 0.48 g.kg) and fat (PRE 1.23 ± 0.4 g.kg; IN 1.02 ± 0.3 g.kg). Significant correlations (P = 0.001) were reported between EA and carbohydrates (PRE r = 0.801; IN r = 0.714); protein (PRE r = 0.675; IN r = 0.769); fat (PRE r = 0.805; IN r = 0.733) and energy intake (PRE r = 0.960; IN r = 0.949). Twenty percent were at risk of disordered eating. This study suggests male elite GF players require education and interventions surrounding nutrition, in particular EA.

How Do Male Football Players Meet Dietary Recommendations? A Systematic Literature Review

The aim of this review was to determine whether male football players meet dietary recommendations according to a UEFA expert group statement and to identify priority areas for dietetic intervention, including training periodization and field position. A database search of PubMed, Web of Science, EBSCO and Scopus was performed. To be included within the final review, articles were required to provide a dietary intake assessment of professional and semi-professional football players. A total of 17 studies met the full eligibility criteria. Several studies showed insufficient energy and carbohydrate intake compared to the recommendations. A majority of athletes consume adequate protein and fat intakes compared to the recommendations. In addition, several studies showed the insufficient intake of vitamins and minerals. This systematic review showed that football players do not meet the nutritional recommendations according to the UEFA expert group statement. Future research should be focused on how to apply nutritional recommendations specific for athletes in accordance with training periodization and positions on the field.

RMR Ratio as a Surrogate Marker for Low Energy Availability

PURPOSE OF REVIEW

Low energy availability (EA) poses severe consequences to athlete performance and overall health. Suppressed resting metabolic rate (RMR) has been observed during periods of low EA. Thus, it has been suggested that the ratio of RMR measured via indirect calorimetry to predictive RMR using a standard predictive equation (RMR ratio) may be a useful assessment of EA in athletes. This review evaluated the use of RMR ratio as a surrogate marker for low EA in athletes and compared methodologies for measuring RMR ratio.

RECENT FINDINGS

Decreased RMR ratio in recent studies often correlates with signs of low EA; however, athletes with less severe cases of energy deficiency may not present with a low RMR ratio. Additionally, the methodology for RMR ratio measurements lacks standardization and varies in recent studies. Use of RMR ratio has promise as a complementary EA measurement when used in combination with other assessment tools.

Prevalence of Surrogate Markers of Relative Energy Deficiency in Male Norwegian Olympic-Level Athletes

The syndrome of Relative Energy Deficiency in Sport (RED-S) includes wide-ranging effects on physiological and psychological functioning, performance, and general health. However, RED-S is understudied among male athletes at the highest performance levels. This cross-sectional study aimed to investigate surrogate RED-S markers prevalence in Norwegian male Olympic-level athletes. Athletes (n = 44) aged 24.7 ± 3.8 years, body mass 81.3 ± 15.9 kg, body fat 13.7% ± 5.8%, and training volume 76.1 ± 22.9 hr/month were included. Assessed parameters included resting metabolic rate (RMR), body composition, and bone mineral density by dual-energy X-ray absorptiometry and venous blood variables (testosterone, free triiodothyronine, cortisol, and lipids). Seven athletes (16%) grouped by the presence of low RMR (RMRratio < 0.90) (0.81 ± 0.07 vs. 1.04 ± 0.09, p < .001, effect size 2.6), also showed lower testosterone (12.9 ± 5.3 vs. 19.0 ± 5.3 nmol/L, p = .020) than in normal RMR group. In low RMRratio individuals, prevalence of other RED-S markers (-subclinical-low testosterone, low free triiodothyronine, high cortisol, and elevated low-density lipoprotein) was (N/number of markers): 2/0, 2/1, 2/2, 1/3. Low bone mineral density (z-score < -1) was found in 16% of the athletes, all with normal RMR. Subclinical low testosterone and free triiodothyronine levels were found in nine (25%) and two (5%) athletes, respectively. Subclinical high cortisol was found in 23% of athletes while 34% had elevated low-density lipoprotein cholesterol levels. Seven of 12 athletes with two or more RED-S markers had normal RMR. In conclusion, this study found that multiple RED-S markers also exist in male Olympic-level athletes. This highlights the importance of regular screening of male elite athletes, to ensure early detection and treatment of RED-S.

Within-Day Energy Balance and Metabolic Suppression in Male Collegiate Soccer Players

Metabolic suppression due to relative energy deficiency can cause various physiological impairments in athletes. The purpose of this study was to evaluate within-day energy balance (WDEB) and the ratio between measured and predicted resting energy expenditure (REE_ratio) and to investigate the relationships between the markers of metabolic suppression. Ten male collegiate soccer players completed a 7-day food diary, physical activity, and heart rate records during the training and rest days. Energy intake (EI) and energy expenditure (EE) were analyzed to evaluate WDEB components. Body composition was measured using dual-energy X-ray absorptiometry (DXA), and blood sampling was conducted for hormonal analysis. The REE was measured using the Douglas bag method and predicted using the DXA-predicted method to calculate the REE_ratio. Participants were categorized into the normal (REE_ratio ≥ 0.94, n = 5) and suppressed (REE_ratio < 0.94, n = 5) groups. There were no group differences in the components of WDEB, except diet-induced thermogenesis (DIT), but EI was significantly higher in the normal group than in the suppressed group (7-day total: 3660 ± 347 vs. 3024 ± 491 kcal/day, p = 0.046 and rest days: 3772 ± 463 vs. 2796 ± 800 kcal/day, p = 0.046). Analysis of hormonal markers of metabolic suppression only showed a significant positive association between insulin-like growth factor-1 (IGF-1) and REE_ratio (r = 0.771, p = 0.009). The relationships between metabolic suppression and the markers of energy deficiency were inconclusive. There are possible associations of insufficient EI and IGF-1 levels with metabolic suppression, and further study is required to understand energy deficiency in male soccer players.