Background: Stress fracture is an injury caused by overuse that exceeds bone capacity. Clinical symptoms are increased pain in the lower extremities during exercise or activities. Bone strength is a risk factor for stress fractures. Bone mineral density contributes to bone strength. Bone mineral density disorders are caused by intrinsic factors and extrinsic factors. Lifestyle is one of extrinsic factors such as inadequate calcium intake, caffeine consumption habits and protein intake. Aim: To know the effect of protein, calcium and caffeine intake on bone density in the incidence of stress fractures in the Selopamioro Yogyakarta State Police School. Method: This research method is quantitative research with cross sectional approach on 18 students of Selopamioro Yogyakarta State Police School. The study was conducted on the 2016 students with 9 students diagnosed with stress fractures and 9 students as the control group. Data were collected from Food Frequency Questioner. Data were analysed using Fisher exact test. Result: Protein intake did not have a significant effect on bone density and the incidence of stress fracture (p> 0.05). Calcium intake has an influence on bone density (p <0.05) but does not affect the incidence of stress fractures (p> 0.05). The habit of caffeine consumption does not have a significant effect on bone density and the incidence of stress fracture (p> 0.05). Conclusion: Less protein intake in the osteopenia group was greater than good protein intake, but did not have a significant effect on bone density and the incidence of stress fractures. Calcium intake has an influence on bone density, but not with the incidence of stress fractures. Caffeine has no effect on both.