Manipulating dietary glycemic index as a means of improving exercise and sports performance

Research in the 1980s showed that exercise capacity could be significantly improved by ingesting carbohydrate (CHO) (Coyle et al. 1983). Since then, a plethora of research has investigated the optimal type, amount, and timing of CHO to maximize endurance performance as well as to optimize adaptation to resistance training (Stellingwerff and Cox 2014). The early 1980s also saw the introduction of the concept of the glycemic index (GI) as a means of classifying CHO types based on blood glucose concentration following consumption (Jenkins et al. 1981). However, it was not until the early 1990s that different GI meals ingested before exercise, were investigated for their role on exercise performance (Thomas et al. 1991). It was proposed that the contrasting exchange lists for CHO might influence the metabolic response and exercise performance outcomes to diets of different GI. However, CHO feeding before, during, and after exercise performance is now generally accepted as a means of improving or recovering from such performance. While high-GI (HGI) meals are also now widely used in the recovery from exercise, the role of HGI compared to low GI (LGI) foods in sports nutrition is still under debate. Taken together, the reviews of Burke et al. (1996), Siu and Wong (2004), Wright (2005), and more recently Donaldson et al. (2010), O’Reilly et al. (2010), and Mondazzi and Arcelli (2009), provide a comprehensive overview of the first 16 years of research in this area. The aim of this chapter is to provide an up-to-date summary and practical application of the evidence regarding GI and exercise performance and the recovery process.