Regular exercise is known to improve insulin sensitivity and metabolic health in people with type 1 and type 2 diabetes, but how exactly does it do this and how should these individuals exercise? We have commissioned a mini-series of reviews to try to answer these questions. Gemmink et al begin this series by providing a muscle-centred view on the beneficial impact of exercise on fat metabolism and, consequently, insulin sensitivity. The authors explain how regular exercise may alter lipid droplet characteristics in the human muscle (and liver) in insulin-resistant individuals, resulting in an ‘athlete-like’ phenotype that is associated with improved insulin sensitivity. Other than the muscle, the liver, adipose tissue, vasculature and pancreas also play a role in the beneficial effects of exercise. Thyfault and Bergouignan explain how exercise activates metabolic changes in these non-skeletal-muscle tissues and how the adaptations can protect against metabolic diseases. So, it is clear that exercise is beneficial for individuals with diabetes, but how in practice should exercise be carried out? In their review, Riddell and colleagues specifically focus on the competitive athlete with type 1 diabetes. They explain the challenges that athletes with type 1 diabetes face in trying to maintain normal glucose levels during training, travel and competition, and how these challenges may be overcome, such as with the use of insulin pumps and continuous glucose monitors. In addition, they discuss how adjustment of carbohydrate intake can improve performance in athletes with type 1 diabetes. Exercise training can also improve glycaemic control in individuals with type 2 diabetes, but it is not known which training regime is likely to elicit the most benefit with regards to this. In their review, Savikj and Zierath discuss how exercise type, intensity and modality affects the impact of exercise on glycaemic control in individuals with type 2 diabetes. They also discuss the impact of nutritional status on exercise-associated benefits, indicating that training with low carbohydrate availability may improve cardiorespiratory function and skeletal muscle oxidative capacity vs conventional training. They conclude that, just like competitive athletes, individuals with type 2 diabetes should be encouraged to adopt training regimens that improve fitness and metabolism.