As the insulin action in T1DM patients differs from that in T2DM, the important questions remaining unsolved are whether or not FOXO1 is activated in non‐obese insulin‐deficient diabetes and whether activation of FOXO1 contributes to cardiac metabolic flexibility with the switch from glucose oxidation to fatty acid oxidation in the myocardium of T1DM. Here, FOXO1 is linked to type 2 diabetes mellitus.