The Association between Olfaction and Taste Functions with Serum Ghrelin and Leptin Levels in Obese Women

Purpose: To investigate the olfaction and taste functions in obese female patients and the association between serum ghrelin and leptin levels compared with healthy controls. Methods: Fifty-two obese women, who have a body mass index >30 kg/m², and 15 healthy women were included in the study. After 8 hrs fasting, blood samples were taken for serum biochemical parameters, ghrelin, and leptin level measurement. For the quantitative assessment of olfactory function, all participants underwent an N-butanol threshold test and odor identification test using 12 Sniffin' Sticks^® fragrance sticks. The gustatory function was tested by administering a whole-mouth above threshold test using sucrose solutions. Results: The sucrose taste threshold score in obese women was significantly higher than the controls (P = 0.004). We found positively significant correlation between serum ghrelin levels and n-butanol threshold scores in obese women (r = 0.300, P = 0.031). N-butanol smell threshold was not significantly different between the two groups (P = 0.149), while the Sniffin' Sticks smell test scores were significantly lower in obese women compared with the controls (P = 0.007). Serum leptin levels were also significantly higher in obese women (P < 0.001) although there was no significant difference in serum ghrelin levels between the two groups (P = 0.768). There was no correlation between serum leptin levels and Sniffin' Sticks scores, n-butanol, and sucrose taste threshold scores in obese women. Conclusions: These results might suggest that leptin, which is an anorexigenic peptide, may have a negative effect on taste and smell functions. More studies are warranted to elucidate the exact role of ghrelin secretion on olfaction and taste functions.