Indeed, it has been shown that, in humans without obesity, sucrose recognition thresholds covaried with diurnal changes in leptin levels such that sensitivity was higher in the morning when leptin levels were lower, and they were lower in the evening when leptin levels were higher; recognition thresholds for other nonsweet tastants did not vary in this manner [86]. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.