Intriguingly, the association with adult obesity is less clear. We investigated by MLPA the parents of the 5 severely obese children carrying the deletion, finding that 4 deletions were inherited (one arising de novo). However, only two of the four adult carriers were obese and there was no significant difference in BMI between the carrier and non-carrier parents (P = 0.15, Student’s t-test). Furthermore, not only were no deletions identified in a total of 840 subjects from adult severe obesity cohorts (a significant difference from the overall frequency for child obesity, P = 0.039), but out of 8 adult carriers from our population cohorts, only 3 were obese. Nevertheless, a further 4 were overweight (BMI ≥25 kg.m−2) so that, overall, adult carriers had a mean BMI of 30.2 kg.m−2 [27.3–33.3], with a mean Z-score (relative to their respective population distributions) of +1.10 [+0.34–+1.86] (P = 9.14×10−4, one-tailed Z-test). The impact of the deletion in terms of BMI is made clear from comparison of the 4 carriers from NFBC1966 and the remainder of this cohort (mean BMI change = +5.8 kg.m−2
