Prolonged wound healing is frequently observed in aged and obese human subjects and is a well known clinical complication, contributing to morbidity and mortality, in advanced diabetes. Genetically diabetic and obese mice have been extensively used as a model to study wound healing impairment, but little information is available on the effect of diet-induced obesity and aging on this process. The purpose of the present study was to investigate the effect of overweight and insulin resistance induced by high-fat-diet (HFD) in middle-aged mice after an excisional cutaneous wound healing. The wound healing process was studied in three groups of male C57/BL6N mice: a) 16 wks old on standard diet (SD-Y group n=10); b) 44 wks old on standard diet (SD-O group n=10); c) 44 wks old on HFD for 39 wks (HFD-O group n=10). Mice were supplied ad libitum with either a HFD (4.7 kcal/g, 49% of calories from fats, 19% from proteins and 32% from carbohydrates) or standard laboratory chow (2.7 kcal/g, 6.5% of calories from fats, 27% from proteins, 60% from carbohydrates and 6.5% fiber).A single full-thickness excisional wound of 4-6 mm in diameter was made in the interscapular region of each animal, with a biopsy punch, exposing the underlying fascia muscularis. Wound area was assessed on day 0 3,7,10 and 14 days after injury. Lesions analysis was performedby Visiolog 6.8 image-processing programon images captured using a digital camera (Nikon D300S). Healing was measured as degree of wound contraction and data were expressed as a percentage of the initial wound area on day 0.Just before the injury, an oral glucose (1.5 g/kg) tolerance test was performed in overnight fasted mice. Skin biopsy specimens were obtained 7 days after injury, and histological sections were prepared and stained with hematoxilin/eosin. Skin samples were blindly scored for the degree of re-epithelialization e, type /amount of granulation tissue and inflammation. Data were expressed as mean ± sem. HFD caused a 42% increase in mice body weight. Obesity was accompanied by development of a distinct insulin-resistance, as shown by the impaired clearance of blood glucose during the tolerance test (AUC from 0 to 120 HFD-O 33256±2573 vs SD-Y 24246±2056 and SD-O 25685±2210). On day 3, the excision of the skin resulted in retraction of the wound significantly higher in young than old mice, SD-Y 170±7% vs SD-O 122% ±7, HFD-O 120±10%. On the other hand, old mice fed the HFD showed a significantly slower wound closure than young and old mice on a standard diet; (wounds size was on day 7 and 10: SD-Y 45±18% and 20±6%; SD-O 45±6 and 13±3%; HFD-O 94±8% and 45±2 % vs day 0). These macroscopic findings were confirmed by histological analysis. On day 7 after injury, young and aged mice, on standard diet, developed abundant and mature granulation tissue which filled the whole wound bed; wounds were mostly re-epithelialized,with presence of moderate amounts of inflammatory cells. On the contrary, mice on a HFD developed scant amount of mature granulation tissue which only partially filled the wound bed. Wounds were only partially re-epithelialized and showed a slightly higher degree of inflammation.This study shows that the maintenance of aged mice on a high-fat-diet is able to reduce glucose tolerance slows down the healing process of an experimentally induced injury, with delayed wound closure, impaired re-epithelialization and prolonged wound inflammation. The delayed wound healing in this group of mice is likely to depend on the induced obesity, and consequent insulin resistance, rather than on the aging process.