A good nutrition plays an important role in physical activity and athletic performance. This study aims to show how poor nutritional and dietary monitoring can cause athletes to lose competitions. This review, through a collection of existing and documented information on athlete nutrition and dietetic will show how they impact positively or negatively on athlete performance and contribute to losing or winning competitions. National and international federations must take their responsibilities to offer a chance of victory to everyone during the various competitions, whether it is an individual or team competitive sport. This can only be done by requiring federations/teams to have specialists in sports nutrition and dietetics or consultants in this area in order to allow athletes to have a fair game, with the same chance of success.