A-T is associated with, among other things, a resistance to insulin, which causes fatty liver and diabetes. This study will recruit people who have A-T, but have not developed diabetes, and compare this group to "healthy" controls, i.e. people who do not have A-T or diabetes. The study will compare how the groups respond to two drugs used to treat diabetes (metformin and pioglitazone), with the intention that this will guide the management of diabetes in A-T.