The prevalance of type 2 diabetes (T2DM) is increasing worldwide. Lipid content in skeletal muscle fibers is higher in T2DM than in control subjects. Intramyocllelar lipid (IMCL) content is negatively associated with insulin sensitivity. However, endurance trained atheletes have IMCL levels simular to patients with T2DM, whilst being insulin sensitive, the so-called athelete’s paradox. Therefore, it has been suggested that lipid intermediates, like diacylglycerol and ceramides, interfere with insuline sensitivity and that total IMCL content is just a surrogate marker of these bioactive lipid intermediates. However, dta in humans is on the involvement of bioactive lipids impeding insulin sensitivity remains contradictory.