RecruitingClinical trialImpact of Obesity on Microvascular Insulin Action and Cardiorespiratory Fitness in Type 1 DiabetesThe purpose of this study is: * To see if insulin resistance (how sensitive your muscle tissue is to insulin) is associated with lower cardio fitness in people with Type 1 diabetes compared to healthy controls, before and after a High Intensity Interval Training (HIIT) exercise program. * To see if being overweight and having Type 1 diabetes is associated with lower cardio fitness compared to overweight healthy controls, before and after a HIIT exercise program.