At the baseline visit an MRI, blood sampling and fat biopsy will take place during the half day visit before the tracer study. This will allow us to assess fat distribution using MRI and obtain adipose tissue to carry out lab-based studies to assess the adipocyte function and response to metformin and pioglitazone. Blood samples are taken for "safety bloods" (i.e. to ensure normal renal function and HbA1c <48mmol/mol) but also for future DNA analysis, to confirm the diagnosis in the A-T group, and to check for carrier status of the controls.