The effect of consuming a diet containing sunflower oil, which was repeatedly used to fry potatoes, on bone mass and biomechanical competence in growing rats, was investigated. Male Wistar rats (21±1 days old) (n=34) were assigned at weaning to one of three diet groups for 8 weeks: those fed a control diet (C; n=10), a sunflower oil (SFO; n=12) diet or a SFO diet which was repeatedly heated (SFOx; n=12); both mixed with a commercial rat chow at weight ratio of 13% (w/w). Zoometrics, food intake, serum fatty acids composition and lipid profile, total skeleton bone mineral density (BMD), bone mineral content (BMC), and femur biomechanical competence were assessed. Animals fed SFOx diet had altered body growth and showed both increased serum total cholesterol (T-chol) and non-high-density lipoprotein cholesterol (non-HDL-chol). SFOx rats also showed marked differences in BMC, their femur and tibiae had the lowest structural and geometrical properties, but material properties were unchanged. This study showed that growing male rats consuming a SFOx diet adversely affected their body growth, and lipid metabolism. Additionally their BMC and bone biomechanical properties were also altered due to modifications in bone geometric design.