In all three samples, the measured BMI (in kg/m2) was assessed for extremeness using age- and sex-specific percentile criteria for the German population (35). According to this reference population, all cases (cases of the case–control sample and offspring of the two family-based samples) were at least overweight (percentile ≥ 90th). Most of the cases were extremely obese (percentile ≥ 97th): 93.6% of the index cases of the family-based GWAS sample, 92.5% of the cases in the case–control GWAS sample as well as 91.5% of the offspring from the family-based replication sample.
