To investigate current theories of the contributing factors to osteopenia/osteoporosis in competitive cyclists, we present a narrative review of published cross-sectional studies investigating plausible etiologies of decreased bone density in competitive cyclists. Aggregate from multiple published studies as cited. Bone mineral density in cyclists appears to be correlated positively to the cumulative amount of bone loading forces experienced over a lifetime. However, decreases in bone mineral density are noted over the short term if bone loading forces are removed, despite previous gains. There also appears to be a negative correlation between bone mineral density and dermal calcium losses during exercise. Data are mixed on whether calcium supplementation improves bone mineral density in this setting. No correlation was found between sex hormones and bone mineral density in the competitive cyclists studied. Knowledge of the underlying contributors to reduced bone mineral density in cyclists can aid in making preventative and therapeutic recommendations that potentially could decrease the morbidity and mortality related to osteoporosis.