FAAH and obesity due to melanocortin 4 receptor deficiency: Interestingly, the sentinel variant for both metabolites was a common (observed MAF = 0.21 in JHS and global MAF 0.21 as reported in the NCBI Allele Frequency Aggregator), missense variant (chr1:46405089C > A; Pro129Thr) that has previously been shown to reduce FAAH stability and enzymatic activity in cell-based model systems and has been associated with overweight and obesity in human studies (17, 18).