Although weight can play a positive or negative role in performance, it's not the only way to improve or destroy performance. Sadly, when athletes start looking at performance and how to get faster, stronger or go longer, weight becomes the only focus.
It's not uncommon for the athlete who wants to achieve a specific body composition to look for strategies and behaviors that are extreme in order to make for quick changes. Because most people won't keep up with new habits if they don't result in quick changes or feedback, many of the strategies that athletes take to change body composition adversely affect health. Fasted training, restricting fluids and calories during prolonged sessions, not focusing on good recovery, eliminating food groups, drastically cutting out calories and not having an all around good relationship with food can cause a host of issues, such as : hormonal disturbances, slow tissue growth/repair, slow energy metabolism, declining energy and excessive fatigue, bone issues, endocrine issues, altered pyschological and physiological functioning and a decline in performance. The athlete who feels the need to make extreme changes in the diet is typically the athlete who will experience the greatest risk to health and performance down the road, if not immediately. In other words, a strong desire to get leaner for performance actually destroys performance, instead of helping it.
Keeping in mind that even short periods of intentional or unintentional food restriction, food group elimination or poor sport nutrition fueling can negatively affect how you train, compete and recover. Poor exercise performance and an increase in injuries and burnout is common in the underfueled and undernourished athlete.
Let a change in body composition be a direct and non-forced result of good nutrition habits and behaviors. By doing a great job of meeting your daily energy needs, focusing on nutrient timing, using sport nutrition properly and not neglecting your health, you'll find yourself with a body composition that you can be proud of because it's the body that is fueled, fit, strong and healthy and ready to perform.
A healthy body performs amazingly well. Instead of making strict changes in the diet in order to change your body image, focus on fueling and nourishing your amazing body.
I never said you can't lose weight or change body composition to boost your performance. But now is not the time to diet (nor is it ever OK to make an extreme change to your diet that isn't sustainable). If your strategies for weight loss or body composition change are counterproductive to your initial goals of being faster, more resilient, healthier, stronger and more powerful or you are unable to meet the athletic demands of your sport with your new lean and toned body, your dietary approaches are not productive.