It is well known that total body mass (BM) is positively associated with bone mineral content (BMC). However, the extent to which BM, fat mass (FM), and lean mass (LM) are related to BMC remains unclear. Considering that chronic loading of a bone is perhaps the most important factor affecting bone mass, evaluation of the relationship between these variables should consider the load placed on segments of the body. Therefore, this study examined the changes in regional body composition (i.e., total body, arms, legs, and trunk) during diet-induced reduction of BM. Seventy obese women (age 48.5 ± 7.8 yr) were randomly assigned to two groups: diet (D, n = 42) and control (C, n = 28). Subjects in group D participated in one dietary counseling session per week and their energy in-take was restricted to 1070 ± 240 kcal/d. BM, FM, LM, and BMC of each segment decreased significantly (P<0.05) except for BMC_. Positive correlations (P<0.05) between percentage change (%change) in BMC and %changes in BM, FM, and LM were observed for every segment except FM_, LM_, and total LM. Comparing the correlations of %changes in BM, FM, and LM to %change in BMC, %change in BM had the highest association with %change in BMC in each segment (r = 0.39 to 0.65). However, in the arms, the correlation between %change in BM_ and %change in LM_ (r = 0.65) was equivalent to the correlation between %change in total BMC and %change in total BM (r = 0.61). These results suggest that BM is the greatest contributor in the loaded segment (i.e., trunk and legs), and LM is also an important contributor in the unloaded segment (i.e., arms).