Elite collegiate swimmers do not meet sport nutrition recommendations during heavy training: effects of sex and within-day nutrient timing

Abstract

Background: Compared to the general population, athletes experience high energy expenditures requiring increased energy and macronutrient intakes to sustain training and optimize performance. While the International Olympic Committee (IOC) and International Society for Sports Nutrition (ISSN) have established recommendations for nutrient intakes, many athletes do not meet the recommended daily allowance (RDA) for the general population, and sport and sex-specific differences are not well documented. Exploration of within-day energy balance (WDEB) shows athletes may achieve energy balance by the end of the day but may present with poor WDEB. Data support that female athletes are at greater risk of nutrient deficiencies than their male counterparts, and it is unclear whether swimmers meet sport-specific nutrient intake and timing recommendations. Following our previous WDEB analysis, the purpose of this investigation was to assess dietary macronutrient intake as related to RDAs (USDA and IOC/ISSN), within-day macronutrient timing, and associated sex differences in swimmers.

Methods: In elite male and female swimmers (n = 25; 18-22 yr), we assessed energy intake (EI), total daily energy expenditure (TDEE), macronutrient intake (fat (FAT), protein (PRO), carbohydrate (CHO)) and timing during heavy training. Frequency analysis was utilized to determine the number of athletes meeting general and athlete-specific RDAs. Repeated-measures ANOVA was used to assess nutrient timing across sex groups.

Results: When compared to IOC/ISSN daily recommendations, only 6/25 swimmers met FAT intake, 7/25 met CHO intake, and 24/25 met PRO intake IOC/ISSN daily recommendations.Males had greater EI and TDEE compared to females (p < 0.05). PRO consumption (% of EI) was a larger percentage of total intake in male vs females (28 ± 5% vs 23 ± 3%; F = 2.996; p = 0.014). No swimmers met CHO recommendations (g⋅kg^-1) pre- or during exercise for the first daily training session. 13/25 met pre-exercise CHO recommendations, while 6/25 and 11/25 met during and post-exercise CHO recommendations for the second training session. Repeated measures ANOVA revealed effects of sex and time on intake (g⋅kg LBM^-1⋅hr^-1) for FAT (Sex; F = 5.659, p = 0.26; time; F = 12.068, p = 0.006) and PRO (Sex; F = 6.719, p = 0.016; time; F = 13.177, p = 0.011). There was a significant sex*time interaction for CHO consumption (F = 6.520, p = 0.017).

Conclusion: The results from this study demonstrate significant sex-differences, indicating that most swimmers meet athlete-specific recommendations for PRO, but not CHO or FAT intake. CHO timing for pre-, during, and post-exercise was met by only 52% swimmers. Results suggest that swimmers should prioritize CHO intake, emphasized around and during training bouts.

Keywords: Nutrient timing; elite athletes; macronutrient intake; swimmers; within-day energy balance.

Figure 1.

Daily distribution of macronutrient intake of all swimmers. Descriptive data of daily consumption of macronutrients are depicted for all swimmers, male and female swimmers. Distributions are presented as percentage of total daily intake, where total daily intake represents 100%. Percentages represent dietary macronutrient composition for two weekdays and one weekend day.

Figure 2.

Macronutrient consumption in all swimmers across the Day. Daily consumption of macronutrients are depicted in red (women) and in blue (men). Data are presented as consumption of specified macronutrient normalized to body weight as grams/kilogram body weight/day. Black boxes indicate swim training sessions. p-values <0.05 were considered significant and denoted in bold. Panel a) CHO consumption across the day. Panel b) FAT consumption across the day. Panel c) PRO consumption across the day. Repeated measures ANOVA revealed a significant effect of sex and time on consumption of macronutrients as grams/day (g⋅d⁻¹⁾ for all macronutrients (CHO, FAT, and PRO), (p < 0.05). There was a significant effect of sex and time on macronutrient intake normalized for body weight as grams/kilogram body weight/day (g⋅kg⁻¹⋅d⁻¹) for all macronutrients (CHO, FAT, PRO), (p < 0.05), and there was a significant sex*time interaction for CHO intake normalized for body weight (p < 0.05). g, grams; g/kg/bw/d, grams/kilogram body weight/day.