# Pre‐Season Total Energy Expenditure and Dietary Intake of Professional Male Soccer Players: A Doubly Labelled Water Study

## TL;DR

This study measured energy expenditure and diet of professional male soccer players during pre-season and found they under-consumed energy and carbohydrates despite consistent training demands.

## Contribution

The study provides novel empirical data on energy expenditure and dietary intake of professional soccer players using doubly labelled water during pre-season training.

## Key findings

- Total energy expenditure was 13.25 ± 1.31 MJ/day with no significant difference between training-only and training-plus-match microcycles.
- Players under-consumed energy and carbohydrates, with no adjustment in intake across different training days.
- Low carbohydrate availability was observed at key meals like breakfast and post-training lunch.

## Abstract

Limited data exist describing how professional footballers meet their energy requirements during pre‐season, a phase characterised by increased training volume and a progressive shift from general conditioning to football‐specific preparation. This study quantified total, resting, and activity energy expenditure (AEE), diet‐induced thermogenesis, water turnover, and dietary intake in six professional male soccer players (age: 25 ± 1 year; height: 182.5 ± 10.1 cm; body mass: 77.8 ± 8.2 kg). Players were studied across 14 consecutive days, representing training‐only and training‐plus‐match microcycles. Total energy expenditure (TEE) was measured using doubly labelled water, resting energy expenditure (REE) by indirect calorimetry and dietary intake using the remote food photography method. Fourteen‐day mean TEE, REE, AEE and water turnover were 13.25 ± 1.31 MJ⋅day−1, 7.96 ± 0.89 MJ⋅day−1, 4.20 ± 1.03 MJ⋅day−1, 5.16 ± 0.66 L⋅day−1, respectively. Physical activity level was 1.67 ± 0.16 AU. Energy, carbohydrate, protein, and fat intakes were 10.95 ± 1.52 MJ⋅day−1, 2.8 ± 0.6 g⋅kg−1⋅day−1, 2.2 ± 0.4 g⋅kg−1⋅day−1, and 1.5 ± 0.4 g⋅kg−1⋅day−1, respectively. Total energy expenditure was not significantly different between training‐only and training‐plus‐match microcycles (+1.89 ± 1.98 MJ⋅day−1; ES = 0.95 ± 1.08; p = 0.100). No significant differences were observed in energy or macronutrient intake across weekly microcycles (p > 0.068) or between days (p > 0.144). Players did not achieve energy balance or align dietary intake with day‐to‐day training demands, suggesting limited nutrition periodisation during pre‐season. These findings highlight the need for practitioners to implement strategies supporting fuelling, recovery and adaptation during this critical phase.

Energy expenditure was similar between training‐only and training‐plus‐match microcycles, meaning players' fuelling requirements remained largely unchanged. Despite this, players still under‐consumed energy and carbohydrate, highlighting a consistent mismatch between demand and intake across pre‐season.Players did not achieve energy balance or meet carbohydrate recommendations, with no meaningful adjustment of intake across rest, single‐training, double‐training or match days, indicating limited nutrition periodisation during pre‐season.Meal‐by‐meal analysis showed low carbohydrate availability at key fuelling windows, particularly breakfast and post‐training lunch, while protein targets were met and fat intake exceeded recommendations. This underscores the need for targeted, periodised fuelling strategies.

Energy expenditure was similar between training‐only and training‐plus‐match microcycles, meaning players' fuelling requirements remained largely unchanged. Despite this, players still under‐consumed energy and carbohydrate, highlighting a consistent mismatch between demand and intake across pre‐season.

Players did not achieve energy balance or meet carbohydrate recommendations, with no meaningful adjustment of intake across rest, single‐training, double‐training or match days, indicating limited nutrition periodisation during pre‐season.

Meal‐by‐meal analysis showed low carbohydrate availability at key fuelling windows, particularly breakfast and post‐training lunch, while protein targets were met and fat intake exceeded recommendations. This underscores the need for targeted, periodised fuelling strategies.