For the average person, achieving a healthy body composition is crucial for overall health and wellbeing, but for an athlete it is paramount to performance. However, with so many conflicting messages about the best dietary and lifestyle approaches for optimal weight management, it can be challenging for a sports person to know where to start. The objectives of this chapter, therefore, are to explore several strategies for achieving a healthy body composition through nutrition, exercise and lifestyle choices. Key differentiations are made between weight and body composition strategies for differing sport and exercise scenarios. In addition to addressing the standard approach of caloric balancing, we also examine physiological contributors to body composition, including genetics, blood sugar regulation, hormonal health, inflammation, stress hormones, and detoxification. Some of these physiological concepts of body composition are then brought to life by the case study of an Olympic sprinter who was transitioning from a period of off-season into a heavy winter training block.