In multivariate analysis, the statistical interaction between the three UCP genotypes accounted for up to 4·1% and 5% of the inter‐individual variation in sACE activity in the HMAR and T1DM studies, respectively, but with the majority of this variation accounted for by the statistical interaction between UCP2‐866G>A and UCP2D/I genotypes (P = 0·001). This evidence concerns the gene UCP1 and type 1 diabetes mellitus.