[Purpose] The purpose of this study was to assess the possible role of physical activities, calcium consumption and lifestyle factors in both bone mineral density and bone metabolism indices in 350 young adult volunteers. [Subjects and Methods] All volunteers were recruited for the assessment of lifestyle behaviors and physical activity traits using validated questioners, and bone mineral density (BMD), serum osteocalcin (s-OC), bone-specific alkaline phosphatase (BAP), and calcium were estimated using dual-energy X-ray absorptiometry analysis, and immunoassay techniques. [Results] Male participants showed a significant increase in BMD along with an increase in bone metabolism markers compared with females in all groups. However, younger subjects showed a significant increase in BMD, OC, BAP, and calcium compared with older subjects. Osteoporosis was more common in older subjects linked with abnormal body mass index and waist circumference. Bone metabolism markers correlated positively with BMD, physically activity and negatively with osteoporosis in all stages. Also, moderate to higher calcium and milk intake correlated positively with higher BMD. However, low calcium and milk intake along with higher caffeine, and carbonated beverage consumption, and heavy cigarette smoking showed a negative effect on the status of bone mineral density. Stepwise regression analysis showed that life style factors including physical activity and demographic parameters explained around 58–69.8% of the bone mineral density variation in young adults especially females. [Conclusion] body mass index, physical activity, low calcium consumption, and abnormal lifestyle have role in bone mineral density and prognosis of osteoporosis in young adults.