Familial resemblance of body composition in prepubertal girls and their biological parents

Background: Heritability estimates for body mass index (BMI; in kg/m²) in children generally have been derived from twin and adoption studies. However, BMI does not reflect total, or regional body composition. Objective: We evaluated the familial resemblance of body composition between prepubertal girls of normal weight and body fatness and their parents by using state-of-the-art technology. Design: The subjects were 101 girls [mean age: 8.5 ± 0.4 y; percentage body fat (%BF): 12-30%] and their biological parents. Weight, height, and body composition [fat mass (FM), fat-free mass (FFM), and %BF] were measured with dual-energy X-ray absorptiometry (DXA) and total body potassium (TBK). Results: Weight, height, and BMI showed low-to-moderate similarity between the girls and both their parents (r = 0.29-0.44. P < 0.01). The girls' FM, FFM, and %BF were significantly related to both parents' body composition. Cross-generational equations were developed for DXA, eg, child's %BF = 12.4 + (0.158 paternal %BF) + (0.145 maternal %BF) (adjusted r² = 0.16, P < 0.001). Regional analysis with DXA showed that the adjusted r² values for the arm, trunk, and leg regions, respectively, were 0.17, 0.33, and 0.31 for lean tissue mass and 0.11, 0.14. and 0.09 for FM. TBK showed a similar relation between parents and girls (r = 0.28-0.47, P < 0.01). Significant heritability (h² ± SE) was detected for BMI (0.35 ± 0.17, P = 0.03) and %BF measured with DXA (0.50 ± 0.12, P = 0.0001). Conclusion: The body composition of prepubertal girls of normal weight and body fatness is significantly related to the body composition of both biological parents.