It is commonly established that macronutrients are categorised into carbohydrates (CHO), proteins and fats, and are required in larger amounts compared to other nutrients. This chapter considers the supply and metabolism of macronutrients within the context of substrate (or ‘fuel’) utilisation during exercise, taking into account current sports nutrition guidelines. Alongside this, we consider the growing interest in personalised nutrition in relation to macronutrient balance, and how this relates to integrative health needs of the athlete, based on their life and exercise demands. This chapter closely aligns with considerations around caloric needs for sport and exercise (Chapter 9), requirements for maximising muscle hypertrophy (Chapter 13), as well as the concept of nutrient timing (Chapter 14). While CHOs are widely regarded as vital for sustained or repetitive high-intensity performance, attention to both quantity and quality of foods are important practitioner considerations in order to optimise athlete health and training benefits, including recovery. Similarly, with long-term interest in high fat or protein strategies to modify metabolic or adaptive responses to training, low-CHO high-fat and ketogenic diets are discussed, as well as high protein strategies. Also considering the translation of research information, it is important to note that most athletes do not (and should not) live at dietary extremes, so practitioners should be mindful of contextually applying relatively balanced dietary macro-nutrition to their athletes.