We have shown that high-fructose diet administered for 8 weeks to adult rats not only induces obesity but also stimulates hepatic de novo lipogenesis and causes hypertriglyceridemia and higher plasma non esterified fatty acids (NEFA). Although about 90% of fructose coming from the diet is metabolised in liver, higher lipid circulation can influence other tissues, such as skeletal muscle. In addition, increased plasma NEFA are considered to be responsible for skeletal muscle mitochondrial derangement and insulin resistance. On the basis of these considerations, we investigated the effect of long term fructose feeding on skeletal muscle mitochondrial energetics and insulin resistance. We assessed mitochondrial mass, respiratory activity and energetic efficiency, together with Western blot analysis of p-Akt/Akt ratio in skeletal muscle from fructose-fed and control rats. The results show increased mitochondrial mass and efficiency of oxidative phosphorylation, that implies a lower level of fuel oxidation. In addition, when p-Akt levels were normalised to insulin plasma levels, significantly lower values were found in fructose-fed rats compared to controls. Therefore, in skeletal muscle, high fructose feeding lowers insulin sensitivity, stimulates mitochondrial biogenesis but induces increased energetic efficiency. This effect could have detrimental metabolic effect by causing energy sparing that contributes to the high metabolic efficiency of fructose-fed rats.