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The primary aim of this study was to investigate whether olfactory detection thresholds are dependent on different states of satiety. Using the threshold test of the Sniffin' Sticks test battery (single-staircase, three alternative forced choice procedure), sensitivity to a non-food odour (n-butanol) and a food-related odour (isoamyl acetate) was investigated. Twenty-four healthy, female subjects (mean age 24.2 years, SD 2.7 years) with normal olfactory function performed the tests when hungry and when satiated. Additionally, they rated their emotional condition, arousal, alertness as well as the intensity and pleasantness of both odorants. No significant change in the detection thresholds for the non-food odour n-butanol, but a significant change in detection threshold for the food-related odour isoamyl acetate was found. The detection threshold for isoamyl acetate was significantly lower in the state of satiety compared to the hungry condition. As expected, the perceived pleasantness of isoamyl acetate was significantly lower in satiety. In summary, the results indicate that in our experimental setting the actual state of satiety has effects on detection thresholds of a food-related odour, but not of a non-food odour. Interestingly, the higher sensitivity was found during the state of satiety challenging the current hypothesis that control of food intake is supported by a decrease in sensitivity to food odours. Instead our findings that satiety decreases the pleasantness of a food-related odour support the hypothesis that both odour threshold as well as pleasantness play an important role in the control of food intake.

The aim of this study was to compare the olfactory performance of anorectic patients and healthy controls with regard to the state of satiety. Using the Sniffin' Sticks, sensitivity to a nonfood odor (n-butanol) and to a food-related odor (isoamyl acetate) was assessed in 12 anorectic females and compared with 24 healthy controls. Threshold tests were performed in a hungry as well as in a satiated state, odor discrimination and odor identification only when satiated. Pleasantness of the odors was recorded. In terms of the non-food odor n-butanol, the olfactory sensitivity of anorectic patients and controls did not differ. Patients with anorexia nervosa had a significantly lower detection threshold for the food-related odor, but only in the hungry condition. Anorectic patients showed significant deficits in odor discrimination and identification, and under-evaluated the pleasantness of isoamyl acetate. Our results suggest an impaired projection from secondary to tertiary olfactory structures in anorexia nervosa, based upon the dichotomy of performance between detection threshold and odor discrimination/dentification. The reduced pleasantness of isoamyl acetate indicates a decreased olfactory responsiveness to food stimuli in anorexia nervosa.