those correlated with the most significant SNPs as done in this paper. Second, for a part of the WHI samples directly genotyped SNPs were only available from a smaller subset of SNPs as genotyping in this subset was based on a GWAS platform and not the dense Metabochip. However, the imputation Rsq as a measurement of the accuracy was very high (Table S1). Third, despite the relative large samples size of over 20,000 AA the statistical significance of the finding is relative weak compared to previous studies in European descent populations for the FTO region. We note that the relative weak power of our study is not due to differences in the observed effect size, e.g. we observed a 1.35% change in BMI per allele for the most significant SNP while the replication stage of Willer et al. [7] observed a 1.25% change in BMI per allele of their most significant FTO SNP (rs9939609). However, the substantially lower allele frequency in AA compared with EA (12% vs. 41%) and the larger variance of BMI in AA populations (e.g. the standard deviation in our study was 6.4 kg/m2 compared with 4.2 kg/m2 in European populations [7] explains the reduce power. Fourth,
