Perceptual and Brain Response to Odors Is Associated with Body Mass Index and Postprandial Total Ghrelin Reactivity to a Meal.

Animal studies have shown that olfactory sensitivity is greater when fasted than when fed. However, human research has generated inconsistent results. One possible explanation for these conflicting findings is metabolic health. Many metabolic peptides, including ghrelin, are moderated by adiposity and influence olfaction and olfactory-guided behaviors. We tested whether the effect of a meal on the perceived intensity of suprathreshold chemosensory stimuli is influenced by body mass index and/or metabolic response to a meal. We found that overweight or obese (n = 13), but not healthy weight (n = 20) subjects perceived odors, but not flavored solutions, as more intense when hungry than when sated. This effect was correlated with reduced postprandial total ghrelin suppression (n = 23) and differential brain response to odors in the cerebellum, as measured with functional magnetic resonance imaging. In contrast, it was unrelated to circulating leptin, glucose, insulin, triglycerides, or free fatty acids; or to odor pleasantness or sniffing (n = 24). These findings demonstrate that the effect of a meal on suprathreshold odor intensity perception is associated with metabolic measures such as body weight and total ghrelin reactivity, supporting endocrine influences on olfactory perception.