Seven of the 32 BMI-SNPs were found to be associated with BMI in the SAGE sample (p < 0.01), which included SNPs in or near FTO and BDNF (Additional file 1: Table S1). The mean number of BMI risk alleles per person was 28.5 (SD = 3.4) with a range from 18 to 39 and the distribution is presented by self-reported ancestry in Figure 1. As shown in Table 2, the SNP-GRSS was highly significantly associated with BMI in the combined sample (p < 1.11×10−12) and accounted for 3.1% of the variance. Examining GRSSs by ancestry indicated that point estimates for effect size and percent of variance accounted for in BMI tended to be greater in EA than AA sample (Additional file 3: Table S3a). However, there were no statistical differences in GRSS effect sizes (p > 0.138) when comparing by ancestry (Additional file 3: Table S3b). Although there were no statistical differences in effect sizes by GRSS method, the proportion of variance in BMI accounted for increased by 0.6-0.9% when using weighted scores and in the EA sample an additional 0.2% when incorporating imputed genotype probabilities (Additional file 3: Table S3c).
