Insulin sensitivity relates to the fatty acid composition of the skeletal muscle phospholipids and the intramuscular triglyceride content. The fatty acid composition of the phospholipids - but not of the triglycerides - in the muscles are influenced by regular physical activity of low-moderate intensity. An increased degree of unsaturation of the cell membranes after training may hypothetically contribute to the improvement of insulin sensitivity. Different ways of reducing the supply of lipids in the muscles may possibly cause similar changes of the fatty acid composition of the cell membranes. Further studies are needed to explore the relationships between changes of the skeletal muscle lipid composition during physical activity, the interaction with dietary fat intake, and changes of insulin sensitivity and development of related metabolic disorders.