Research has demonstrated that individuals with eating disorders have an impaired sense of smell and taste, though the influence of eating attitudes, dietary restraint and gender in a non-clinical sample is unknown. In two studies (study 1: 32 females, 28 males; study 2: 29 females) participants completed questionnaires relating to Eating Attitudes (EAT) and dietary restraint (DEBQ) followed by an odour (study 1: isoamyl acetate, study 2: chocolate) threshold and taste test. In study 2 we also measured the number of fungiform papillae taste buds. Study one revealed that increases in pathological eating attitudes predicted poorer olfactory sensitivity (males/females) and lower bitterness ratings for the bitter tastant (females only), suggestive of poorer taste acuity. In study two we found that both eating attitudes and restraint predicted poorer sensitivity to an odour associated to a forbidden food (chocolate) and that increasing eating attitudes predicted higher sweetness ratings for the bitter tastant. Interestingly increases in restraint were associated with an increased number of fungiform papillae which was not related to bitter or sweet intensity. These findings demonstrate that in a young healthy sample that subtle differences in eating pathology and dietary restraint predict impaired olfactory function to food related odours. Further that perception of bitter tastants is poorer with changes in eating pathology but not dietary restraint.
In western societies, eating related disorders are among the most frequently reported health problems in young females (Grave, 2011). The seriousness of conditions such as anorexia nervosa is underlined by the fact it has the highest mortality rate (≈20%) of any psychiatric illness (Vitiello & Lederhendler, 2000). The precise causes of eating related disorders are still unknown but are likely a combination of psychological, environmental and biological factors (Grave, 2011). To further understand this complex condition, the role of smell and taste function has also been investigated. At the clinical end of the spectrum, work has shown evidence for anorexics to have an impaired sense of smell (Aschenbrenner et al., 2008, Rapps et al., 2010 and Roessner et al., 2005) and taste (Aschenbrenner et al., 2008, Casper et al., 1980 and Rodin et al., 1990). However, in non-clinical samples it is unclear whether more general attitudes relating to eating behaviour are also associated with differences in smell and taste function. Attitudes relating to eating behaviour can be measured with instruments such as the Eating Attitude Test (EAT) (Garner & Garfinkel, 1979) which contain a series of questions relating to eating behaviour, with scores over a certain threshold, typical of individuals with eating disorders. Using the EAT, work has shown across a sample of hospitalised anorexic, bulimic and control subjects that EAT scores were negatively associated to olfactory function; that is, those with more disordered attitudes toward eating had a poorer sense of smell (Aschenbrenner et al., 2008).
Apart from the link between the chemical senses and pathological eating attitudes, it is also important to examine more subtle differences such as dietary restraint.
Dietary restraint is believed to be an important component of the maintenance and perhaps development of eating related disorders (Brewerton et al., 2000 and Polivy and Herman, 1993). Very few studies have examined smell and taste function in this population, though one study reported no differences in response to a neutral odour between restrained and unrestrained eaters (Kemmotsu & Murphy, 2006). From a different perspective, work has examined the effect of food odour cues (pizza or cookies) on subsequent hedonics and consumption of those same foods (Fedoroff, Polivy, & Herman, 2003). Results revealed that restrained eaters consumed more of the food that was congruent with the odour cue, i.e. more pizza was eaten when preceded by the pizza compared to cookie odour cue. This pattern was not observed in unrestrained eaters and therefore suggests that restrained individuals were more sensitive to food odours, at least in their effects on subsequent food consumption. We are not aware of any research examining differences in taste in these populations.
To summarise, there is evidence for poorer olfactory/gustatory function in anorexics/bulimics, but it is unclear whether differences in Eating Attitudes (EAT) and dietary restraint might predict smell & taste function in a non-clinical sample. We also wished to examine whether associations are evident in both male and female samples. Historically, eating disorders and dietary restraint are thought of as applicable to mainly females, but there is evidence of a convergence of eating disorder prevalence between males and females (Woodside et al., 2001); which therefore make it important to look at both genders.
Additionally, the above research (Aschenbrenner et al., 2008, Kemmotsu and Murphy, 2006, Rapps et al., 2010 and Roessner et al., 2005) has not examined olfactory sensitivity using a food related odour, which given the topic under investigation would seem particularly important.
In the present study, individuals completed measures of eating pathology (EAT) and dietary restraint (DEBQ) followed by an olfactory threshold test to a food related odour (banana/pear: isoamyl acetate) and finally a taste test to bitter and sweet tastants. We tentatively predict that for females, increases in EAT and DEBQ will be associated with poorer olfactory and gustatory function. Since we are not aware of any previous research in males, our aim is mainly exploratory. Finally, we included measures of BMI and hunger state, since research has shown that these factors can influence olfactory sensitivity (Stafford & Welbeck, 2011).
In study 2, we extended the research to examine the effect of using a food odour (chocolate) with particular relevance to those with eating disorders (Knight & Boland, 1989) as there is reason to believe that sensitivity to these odours might actually increase with eating pathology.
