A number of questions need to be answered before nutritional advice can be given to an athlete. How much fuel (energy) does a sportsperson need? Which fuels are preferred? What about the proportion between carbohydrate, fat and protein? What roles do the vitamins and minerals play? In this article more information on the energy needs.
Physical activity requires energy. Therefore a sportsperson often needs more energy than a more sedentary person who sits most of the day. The daily energy requirement of a sportsperson depends on a number of factors, such as type of sport, goals, training and competition schedules and other lifestyle and occupational activity. During the more active phases, energy requirements are higher than during less active periods, for example during rest days, holidays or when injured. In the case of more frequent exercise, a lower energy intake (< 1,800 – 2,000 kcal per day) may lead to weight loss and diminished functioning which can have a negative effect on training or sports performance. (1-2)
The starting point is that the sportsperson takes in sufficient energy to train well, keep a stable weight and to maintain the desired body composition in terms of muscles and fat mass and bone density. This differs for each sportsperson.
Estimating energy needs
In order to determine energy requirements the individual energy needs at rest (Resting Energy Expenditure or REE) and the level of physical activity should be assessed. The REE is dependent on weight, height and age and there are different methods available to calculate this. The level of physical activity is represented by the PAL value, whereby PAL stands for ‘physical activity level’. Active athletes have an average PAL value of 1.8. (3)
The European Food Safety Authority (EFSA) defined Dietary Reference Values (DRVs) for energy in 2013 providing recommendations for average energy requirements for men and women and different age groups. The basis of the average energy requirement is the Resting Energy Expenditure (REE) calculated in accordance with the Henry equation (Henry, 2005). Subsequently EFSA calculated average energy requirements for each age group at four different activity levels (PAL values) shown in table 3 (3).
Energy sources during exercise
In the case of short duration exercise (3-5 minutes) the energy source is predominantly adenosine triphosphate (ATP) and creatine phosphate present in the muscles. In addition, glycogen stored in muscles can be used as an energy substrate without oxygen and is called anaerobic metabolism.
Aerobic metabolism (which requires oxygen) of glycogen from liver and muscles supplies the body with energy for longer duration exercise. During physical activity lasting 1 to 4 hours at 70% of the maximum oxygen uptake around 50-60% of the energy is released from carbohydrate. The rest comes from metabolism of fat.
During metabolism of carbohydrates in the muscle cells more energy is released per time unit than from metabolism of fats (1). Therefore carbohydrates are referred to as a ‘fast’ fuel and fats a ‘slow’ fuel. During low intensity exercise, energy is supplied by both carbohydrates and fats, whereas during more intense exercise a higher proportion of energy is supplied by carbohydrates. Training can improve the capacity to oxidise fat during exercise, which allows for a greater use of fat as an energy source. The advantage of this is that the supply of muscle glycogen will be depleted less quickly and the exercise can continue for a longer duration. (1,2,4)
Publication Sport & NutritionWhat does science say about the role of nutrition in sports performance?
- American College of Sports Medicine, Academy of Nutrition and Dietetics and Dietitians of Canada. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016; 116: 501-528.
- IAAF Athletics (2013). Nutrition for athletics. A practical guide to eating and drinking for health and performance in track and field. Updated May 2013. International Olympic Committee (2010). Consensus Statement on Sports Nutrition 2010. http:// www.Olympic.org/Documents/Reports/EN/CONSENSUS-FINALV8-en.pdf. Accessed November 6, 2011.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) (2013). Scientific Opinion on Dietary reference values for energy. EFSA Journal 2013;11 (1): 3005. www.efsa.europe.eu/efsajournal
- Loon van L.C.J. (2013). The human engine.