As noted above, a significant association with obesity of deletions of the SH2B1 locus was identified by quantitative analysis of BMI in the NFBC1966 population cohort alone, Thus, the reduced sample size was compensated for by inclusion of subjects with intermediate phenotypes (i.e. overweight) and the increase in statistical power that derives from analysis of quantitative traits compared to case-control approaches to association testing; indeed, this advantage becomes progressively more marked at lower allele frequencies for the genetic marker under test [22]. Here, SH2B1 is linked to obesity due to melanocortin 4 receptor deficiency.