Almost Nothing - Not Even Bariatric Surgery for Obesity - Changes Olfactory Sensitivity

Abstract

Altered olfactory functions in patients with eating disorders have been reported with obesity, during hunger, following food ingestion and after bariatric surgery, but subsequent data have remained controversial. Methods : We investigated olfactory function (threshold, identification, discrimination) by Sniffin Sticks® in six independent studies: At baseline and 24 h and 48 h after a zero-calorie fasting (Study 1); fasted and after a 3810 kJ mixed meal (Study 2); twice after a 2510 kJ mixed meal supplemented with either 40 g saturated or unsaturated fatty acids (Study 3); prior to and after rotation-induced nausea (Study 4); at baseline and after a 5-day 6° head-down tilt bedrest (HDT-BR) and a high (7.7 mmol/kg BW/d) and low (0.7 mmol/kg BW/d) sodium diet (Study 5). We also compared odor sensitivity before and 12 months after bariatric (sleeve) surgery in patients with morbid obesity (Study 6). Results : Fasting (Study 1) did not alter olfactory functions, and a highcalorie diet (Study 2) moderately improved odor discrimination only; saturated fatty acids (Study 3) marginally improved odor identification, while the induction of nausea (Study 4) did not affect olfaction. HDT-BR (Study 5) significantly reduced the olfactory thresholds as well as the total score, mainly due to the bedrest component. Bariatric surgery (Study 6) did not change odor sensitivity, but some morbidly obese patients exhibited abnormally low olfactory functions prior to and after surgery. Conclusions : Manipulation of the hunger/satiety state has only marginal effects on olfactory functions in normal healthy volunteers and obese patients.