Skeletal muscle plays a major role, together with the liver and body fat tissues, in regulating metabolism. Skeletal muscles make up the body’s protein deposits and store more than 80% of its glucose reserves. Almost all muscles contain two types of cells, called primary and secondary muscle fibres. The latter can be divided into oxidative (which use mainly fatty acids at rest) and glycolytic (which use mainly glucose). The number of primary cells is genetically predetermined and barely affected by environmental influences. In contrast, secondary fibres are sensitive to environmental conditions, such as the metabolic environment within the uterus. Should the number and the activity of oxidative fibres be restricted during the prenatal phase, because of metabolic conditions within the uterus, this will have an impact on a child’s metabolism both immediately and later on in adult life.