APBA1 and obesity due to melanocortin 4 receptor deficiency: The effect of BSN on BMI was larger than that of any previously reported ExWAS gene (Fig. 2) and substantially increased the risk of obesity (BMI > 30 kg m−2) in UK Biobank (BSN: odds ratio (OR) = 3.04 (95% confidence interval (CI), 1.87−4.94), P = 7.7 × 10−6, 49% case prevalence; APBA1: OR = 2.14 (1.46−3.13), P = 8.5 × 10−5, 41% case prevalence) and for BSN also increased the risk of severe obesity (BMI > 40 kg m−2) (OR = 6.61 (3.01−14.55), P = 2.6 × 10−6, 11% case prevalence) although this was not the case for APBA1 (OR = 1.91 (0.70−5.19), P = 0.20, 4% case prevalence; Fig. 3).