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Unformatted text preview: Energy balance and body composition in sports and exercise ANNE B. LOUCKS * Department of Biological Sciences, Ohio University, Athens, OH 45701-2979, USA Accepted 7 August 2003 Many athletes, especially female athletes and participants in endurance and aesthetic sports and sports with weight classes, are chronically energy deficient. This energy deficiency impairs performance, growth and health. Reproductive disorders in female athletes are caused by low energy availability (defined as dietary energy intake minus exercise energy expenditure), perhaps specifically by low carbohydrate availability, and not by the stress of exercise. These reproductive disorders can be prevented or reversed by dietary supplementation in compensation for exercise energy expenditure without any moderation of the exercise regimen. Energy balance is not the objective of athletic training. To maximize performance, athletes strive to achieve an optimum sport- specific body size, body composition and mix of energy stores. To pursue these objectives, athletes need to manage fat, protein and carbohydrate balances separately, but it is impractical for athletes to monitor these balances directly, and appetite is not a reliable indicator of their energy and macronutrient needs. To guide their progress, athletes need to eat by discipline and to monitor specific, reliable and practical biomarkers of their objectives. Skinfolds and urinary ketones may be the best biomarkers of fat stores and carbohydrate deficiency, respectively. Research is needed to identify and validate these and other markers. Keywords : biomarker, body composition, energy balance, exercise, reproduction, sport. Introduction This article updates, but does not replace, the excellent chapter on the state of knowledge about energy balance in sports in the Proceedings of the 1991 IOC Consensus Conference on Foods, Nutrition and Sports Performance (Westerterp and Saris, 1991). That chapter made four main points that warrant additional commentary in the light of experience since that conference. The first of those points was one that would appear to most people to be obvious: that total energy intake must be raised to provide the energy expended during athletic training and performance. As will be described in more detail below, many athletes, but female athletes in particular, do not do so. The second point was one that many had taken for granted: that maintenance of energy balance in athletes can be assessed by monitoring body weight, body composition and food intake. In practice, these techniques have not led to confident assessments of energy balance, again especially in female athletes. The third point was that in sports in which low body weight is advantageous for performance, many athletes, and again especially female athletes, practise weight loss techniques that place their reproductive and skeletal health as well as performance at risk. Athletes in such sports were cautioned to lose weight gradually. Recent research has identified lowweight gradually....
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This note was uploaded on 04/04/2009 for the course NUTRITION 705 taught by Professor Buell during the Spring '09 term at Ohio State.
- Spring '09
- The Land