We have identified four potential loci associated with BMI in African Americans but none of these loci have been reported in prior GWAS. Moreover, among 22 SNPs from 17 BMI loci previously identified predominantly in European-derived populations (14–16), none of them showed associations in our GWAS (P > 0.05), except for a nominal association of MC4R rs17782313 (P = 0.02 with negative effect size for the European effect allele) (data not shown). The sample size of our GWAS alone has modest power to detect weak effect sizes. Assuming an effect size of 0.1 s.d. unit of BMI for a BMI-increasing allele with a frequency of 0.5 under the additive model, such as those reported for FTO in Europeans (7), we have only 17% power to detect association at α level of 1 × 10−4. Although the absence of association in European-identified loci in this study may be due to lack of power, these loci have demonstrated inconclusive association with BMI in African Americans (23,25,38), which may reflect allelic (39), locus heterogeneity and difference in linkage disequilibrium in African American as
