The protective effects of hemizygous MAP3K15 PTVs toward both HbA1c (BMI unadjusted: β = −0.21 SD units, 95% CI: [−0.15, −0.26], P = 1.2 × 10−11; BMI adjusted: β = −0.21 SD units, 95% CI: [−0.15, −0.26], P = 4.7 × 10−12) and diabetes (BMI unadjusted: OR = 0.65, 95% CI: [0.48, 0.85], P = 0.001; BMI adjusted: OR = 0.62, 95% CI: [0.47, 0.83], P = 0.001) remained consistent even after adjusting for BMI, demonstrating that the protective effects of losing MAP3K15 are unlikely to be due to differences in adiposity and are likely to benefit individuals irrespective of BMI. This evidence concerns the gene MAP3K15 and diabetes mellitus.