Acute and chronic energy deprivation improves smell performance and heightens the rewarding value of food: How modality of deprivation differently impacts olfaction, food reward, appetite, peptide hormones, and energy intake.

摘要

The study of feeding behavior, and in particular the study of subjective hedonic experience and objective measures of motivation, are central to understanding how appetite regulation can be compromised in certain individuals. Furthermore, with an integrated picture of physiological and behavioral changes that can occur as a result of energy deprivation what emerges is a better understanding of how palatable food can disrupt attempts at regulating body weight at lower levels of body energy stores. In Article I, the genetic association study examining a potential role for a dopamine-related polymorphism in weight loss, it was shown that contrary to the main hypothesis there was no association between TaqIA polymorphism and the amount of body weight loss. In Article II, it was shown that palatability and olfaction ratings increased as a result of a 24 hour fast and females demonstrated larger improvements in overall olfactory performance. Initial body weight was positively related to improved odor detection threshold and total odour score (TDI). Using the same population sample as Article II, Article III highlights that higher sensitivity to reward and disinhibition scores correlated with responding for palatable snack food stimuli in the relative-reinforcing value of food (RRV) task, further indicating that RRV has strong ties with impulsivity. There was a demonstrable lack of negative alliesthesia under the fasted condition where, after a 75% increase in ad libitum energy intake (EI) relative to the fed condition, this greater amount of food consumed was still rated as being more palatable than the lesser amounts consumed under the fed condition. In Article IV it was shown that an equicaloric (-25%) energy deficit by diet alone was a greater challenge to appetite regulation and resulted in greater compensatory increases in EI than deprivation by exercise alone. Independent of deprivation modality there were significant improvements in odour threshold scores. TDI score increased only under diet alone; furthermore, the noted increase in mean TDI score was positively related to increased ad libitum EI. The picture that emerges is that, acutely, a complete fast has more pronounced effects on appetite and ad libitum EI than dieting alone, which in turn had greater effects than exercise alone or controls. Also, TDI improved under all three methods of energy deprivation, but moreso under conditions of deprivation by diet alone.