In order to create a GPS, we obtained the average effects for each of 2,100,302 genetic variants on BMI from the largest published GWAS study of obesity to date (Locke et al., 2015). We used a recently developed computational algorithm to reweight each variant according to the effect size and strength of statistical significance observed in the prior GWAS, the degree of correlation between a variant and others nearby, and a tuning parameter that denotes the proportion of variants with non-zero effect size (Vilhjalmsson et al., 2015). Because the best choice of this tuning parameter is difficult to know a priori, a range of 5 values was tested as previously recommended (Vilhjalmsson et al., 2015).
