Bone composition in adulthood is largely established during growth and is influenced by changes in weight and body composition. Sub-optimal bone composition is determined by increased fracture risk. High fracture rates in osteoporotic and anorexic populations are associated with low bone density, high bone marrow fat to water content, and low bone marrow fat unsaturation. However, obese children, who have increased bone density, are also over-represented in fracture groups, which may be an early indicator of skeletal insufficiency. We examined bone mineral content (BMC), bone mineral apparent density (BMAD), BMAD per unit mass, and bone marrow fat composition to evaluate the differences in bone and bone marrow between healthy-weight and obese children. Participants included healthy-weight (n=10, 15th percentile<BMI<85th percentile) and overweight/obese (n=12, BMI>85th percentile) preadolescents, ages 8–12 years old. BMC and BMAD were measured using dual-energy x-ray absorptiometry (DXA), which is used clinically for assessing fracture risk. Bone marrow fat composition was measured using magnetic resonance spectroscopy (MRS) in the right diaphyseal femur at long echo times (TE). Overweight and obese children had higher BMC and BMAD than healthy-weight children, but low density for their weight, suggesting the strength of their bones may not be sufficient for the loads placed on them. The results showed trending increases in both saturated and unsaturated fatty acid composition in the overweight and obese group, suggesting compromised bone health or an earlier maturation of bone. Saturated fatty acids are known to promote osteoclastic differentiation and bone resorption while unsaturated fatty acids are responsible for decreasing bone resorptive activity, demonstrating the complexities of bone marrow composition as having both detrimental and protective effects on obese bone. This study emphasizes the need for further research into the relationship between bone and bone marrow in order to understand the mechanisms behind achieving optimal bone composition.