Food appeal and desire to eat were correlated, but their differential relations with individual characteristics and different overall mean ratings indicate that participants discriminated between the two constructs despite using the same type of metric to measure them. The present results for appeal and desire to eat dovetail previous reports differentiating liking from wanting [17
], and wanting's relation to weight status [19
]. The consistency in these findings is encouraging given previous studies used different methods (i.e., button pushing vs., asking desire to eat) and terms (i.e., 'liking' v. 'food appeal'). This suggests these measures are capturing aspects of the same construct and confirm the ability for individuals to reliably differentiate between liking and wanting. However given the current lack of a gold standard, the ability to empirically test this notion is unavailable. Results from the present study suggest that the distinction between appeal and desire might be moderated by weight status. For example, BMI was positively related to desire, but not appeal ratings. This suggests that desire to eat a food item could play a larger role in the dysregulation of weight status relative to the food's preference. However, to date, the majority studies evaluating liking and wanting are cross-sectional and few involve food [17
]. Therefore future studies should consider prospective designs to demonstrate the relations between liking and wanting, habitual intake and weight gain.
We observed that BMI was positively associated with desire to eat discretionary foods, however ratings for these foods had no association with hunger or fullness. This could suggest that overweight individuals' desire to eat highly palatable foods is "overriding" homeostatic mechanisms that control food intake (i.e., satiation). These results dovetail previous theories of the development of obesity where overweight individuals' eat for pleasure [19
], consume energy dense foods in response to hedonic hunger [40
], and are highly susceptible to environmental food cues [41
The current data demonstrate that as lean individuals' restraint increases, their desire to eat a highly palatable food decreases. Overweight individuals' dietary restraint did not relate to their desire to eat a food, despite overweight individuals reporting slightly higher levels of dietary restraint. Notably, dietary restraint scores have been previously reported to be unrelated to measures of acute [42
] or habitual intake [44
] but were positively related to increases in weight [46
] and onset of binge eating and bulimia [48
]. Further, restraint has been previously reported to be positively associated with activity in reward-related brain regions when shown images of preferred foods [50
] and when receiving a palatable food [51
], suggesting the more restrained an individual is, the more pleasure they receive from seeing and/or consuming that food. In light of these findings it has been hypothesized that overweight individuals in particular can perceive themselves as 'restrained', but still habitually overeat [52
]. Collectively, data from the present study support this notion, specifically that overweight individuals reported being restrained eaters, but that has no effect on their desire to consume food.
Contrary to our hypotheses we found that the fruit category was rated higher than all other food categories in both appeal and desire and we observed that energy density was inversely related to the ratings. Individuals are born with an innate preference for sweet [53
] and thus it is possible that there is inborn predisposition for the higher ratings of fruit. It is also possible that the colorful nature of fruit could be responsible for its high rating. It is a possibility that fruit was rated higher than other food categories due to a response bias given fruit is generally perceived as healthy. However, if this notion held true across the food categories, one would anticipate that vegetables would also be rated higher. The seasonality of fruit could influence these ratings, because fruit's appearance, taste and cost vary by the time of year. However, a seasonality effect is unlikely given data collection occurred from late summer to mid-winter spanning multiple seasons.
Additional analyses by food categories revealed that only the two 'sweetest' tasting and highest rated food categories, (discretionary foods and fruits) were not associated with hunger or fullness. These findings suggest that discretionary foods and fruits might be foods commonly eaten outside of hunger. Eating despite feeling full can play a role in excess calorie consumption and weight regulation [54
Hunger and fullness were associated with desire to eat, but not food appeal ratings. This could be a result of food appeal being a more stable trait-like characteristic whereas desire to eat could assess a particular state at that point in time specifically influenced by the satiating effects of the nutritional shake consumed prior to the ratings. Because participants were feeling full, they might want to consume a food less, but that food item is still appealing. Because fullness is a transient state and the participants were asked to rate their desire at that point in time, we suggest that individual's interpreted desire to eat as an immediate sensation (e.g., "I want this food right now"), whereas appeal was more of a generalized, stable feeling. Finlayson and colleagues reported differences in liking and wanting ratings when individuals were in differing energy states [16
]. Therefore, we hypothesize that if our study were replicated in the fasted state, ratings for desire to eat would be more similar to food appeal. This hypothesis raises the question of whether appeal and desire originate in the same manner. Preference (similar to food appeal) is developed, in large part, via repeated exposure and physiological learning [58
], but it is unclear how individuals develop desire (or wanting).
It is important to acknowledge limitations in the present investigation. First, there are multiple sensory inputs and feedback mechanisms responsible for eating behavior. This study specifically focused on the individual's response to the visual food cues while controlling for energy state, independent of smell and taste. Because the participants' did not actually taste the food, the results rely on their previous experiences with the presented foods; future studies ideally should measure responsivity to taste. However, this is a considerably more challenging study design when attempting to present and taste a large number of foods, which invoke effects of satiety. Further, visual food cues contribute to food selection and meal initiation and thus can be thought of as anticipatory cues to consumption. Food intake and weight regulation are complex processes and the present results should not be over generalized. Additionally, while there was support (that is, statistical significance) for our hypothesis that overweight individuals would rate larger portions higher than smaller portions, the effects were very small (2-3 points; scale range 0-100). Therefore, the public health significance and generalizability of these results is limited. While we have reported differential effects of portion size on intake by weight status [35
] null effects have also emerged [5
]. Lastly, the validity of using of VAS across group comparisons (e.g., lean vs. obese, male vs. female) has been questioned [60
]. Specifically, the anchors used in VAS may denote systematically different perceived intensities to the different groups. The present results using across group comparisons should be interpreted with caution and future studies should consider the use of generalized labeled magnitude scale as described by Bartoshuk and colleagues (2004).