No evidence of large differences in mother-daughter and father-son body mass index concordance in a large UK birth cohort

It has recently been suggested that there are substantial differences in mother–daughter and father–son associations of body mass index and obesity among contemporary UK children, but much larger studies of older cohorts have failed to find evidence of substantial sex-specific effects. We have tested this hypothesis using the Avon Longitudinal Study of Parents and Children, a large contemporary cohort. Our analyses are based on 4654 complete parent–offspring trios (2323 with male offspring and 2331 with female offspring, all aged approximately 7.5 years). We found maternal body mass index to be a little more strongly associated with female than with male offspring body mass index (β=0.18 (95% confidence interval 0.16–0.20) for females vs 0.13 (0.12, 0.15) for males). However, associations between paternal body mass index and male compared with female offspring were very similar (β=0.16 (0.14, 0.19) for females vs 0.15 (0.12, 0.17) for males). Hence, our study suggests that there is no compelling reason to integrate the belief that there are large differences in parent–offspring body mass index associations with obesity prevention strategies.