How to estimate an athlete’s energy requirements
Adequate nutrient intake is the foundation of an athlete’s diet: it supports optimal body function and delivers the required amounts of macro- and micronutrients. Energy intake from food, fluids and supplements can be estimated with a food diary (usually over 3-7 days), a 24-hour dietary recall or a food frequency questionnaire. All of these methods have built-in limitations and tend to underestimate intake.
An athlete’s energy requirements depend on the training cycle and the competition calendar. They can change from day to day and across the whole training year as training load and intensity shift. Factors such as stress, fear, altitude, hot or cold conditions, physical injury, certain medications and stimulants, and an increase in lean body mass can all raise energy needs.
Energy balance occurs when total energy intake (TEI) equals total energy expenditure (TEE), which is the sum of:
basal metabolic rate (BMR),
the thermic effect of feeding (TEF),
the thermic effect of activity (TEA).
BMR can be calculated with the Cunningham or Harris-Benedict equation, or with the formulas and values in national dietary reference standards (in Poland, the 2017 nutrition standards for the Polish population). Applying the appropriate physical activity level (PAL) then allows TEE to be estimated.
Energy in football nutrition
Energy needs in boys and men vary with physical activity level, body mass and age. Football nutrition has to reflect the fact that energy and metabolic demands change with the stage of the season, the type of training and individual characteristics.
A typical match or training session is assumed to cost between 1,000 and 1,500 kcal, depending on its duration and intensity. Average energy expenditure during a match has been estimated at around 1,107 kcal. On a training day, energy needs range from 3,442 to 3,824 kcal. This is supported by a 2017 study by Anderson and colleagues, which found average energy requirements of 3,566 kcal.
Protein in a footballer’s diet
Dietary protein and training together affect many processes in the body. They act both as the trigger and the building material for the synthesis of contractile and metabolic proteins, and they stimulate structural adaptations in non-muscle tissues such as tendons and bones. Footballers need an adequate protein intake every day to support protein synthesis and recovery.
According to the 2016 joint position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine, athletes should consume 1.2 to 2 g of protein per kilogram of body mass. Higher values are appropriate during periods of intense training or weight loss, and lower values on rest days. The International Society of Sports Nutrition takes a similar position, recommending 1.4 to 2 g per kilogram of body mass.
Carbohydrates: the key fuel in football
Carbohydrates are considered especially important in sport, and in football in particular, because adequate intake ensures optimal muscle glycogen levels. Current recommendations call for high carbohydrate availability before, during and after a match to keep muscle glycogen high.
According to Burke et al. (2011), athletes need 3 to 12 g of carbohydrate per kilogram of body mass, depending on training duration and intensity:
light or technical training: 3-5 g/kg,
moderate-intensity training lasting up to one hour: 5-7 g/kg,
moderate- to high-intensity training lasting 1-3 hours: 6-10 g/kg,
training lasting over 4-5 hours: 8-12 g/kg.
FIFA recommends 5-8 g/kg for moderate-intensity training and 10-12 g/kg for high-intensity training. Oliveira et al. reached similar conclusions, recommending a daily intake of 5-10 g/kg. Polish dietary standards set the recommended share of carbohydrates at 45-65% of energy intake for both boys and men.
What research says about carbohydrates in football nutrition
One study highlighted the role of carbohydrates for footballers. Players on a high-carbohydrate diet had higher muscle glycogen concentrations than those on a normal diet. Before the match, at half-time and after the match, muscle glycogen in the high-carbohydrate group was 15, 4 and 1 g per kilogram of wet muscle, respectively. In the normal-diet group, it was 7, 1 and 0 g per kilogram of wet muscle.
Players on the high-carbohydrate diet also covered more distance than the control group:
high-carbohydrate diet: 6,100 m in the first half, 5,900 m in the second; 27% walking, 24% sprinting,
normal diet: 5,600 m in the first half, 4,100 m in the second; 50% walking, 15% sprinting.
Unfortunately, footballers tend to eat too little carbohydrate over the course of the day.
