TAS1R3 and obesity due to melanocortin 4 receptor deficiency: Although we did not measure T1R2 gene expression, high-fat feeding and increases in body weight/adiposity result in changes in only T1R3 gene expression with associated differences in sweet perception, with no changes in T1R2 expression [37], [38], indicating that diet- and obesity-induced changes in sweet taste sensitivity are likely due to changes in the T1R3 subunit of the sweet taste receptor.