Commentary: Cafeteria diet impairs expression of sensory-specific satiety and stimulus-outcome learning

(2015) Commentary: Cafeteria diet impairs expression of sensory-specific satiety and stimulus-outcome learning. Front. Psychol. 6:536. Current global estimates indicate that the proportion of adults meeting the criterion for overweight and obesity is 40%, with this proportion expected to increase (Ng et al., 2014). Thus, diet is arguably the largest controllable factor related to the burden of disease, yet changing dietary habits is notoriously difficult (Caballero, 2007) and the reason for this is unknown. Mounting evidence suggests that, in addition to contributing to the unprecedented rates of obesity worldwide (Caballero, 2007), the consumption of high fat, high sugar (HFHS) diets is associated with a range of cognitive impairments in humans (Smith et al., 2011; Gustafon et al., 2012) and non-human animals (Beilharz et al., 2014; Reichelt et al., 2015). Such data raise the possibility that intake of calorically dense foods may alter cognitive capacities critical for food-related decision making and, as a result, make it more difficult for individuals to change their eating behaviors. In a recent issue of Frontiers, Reichelt et al. (2014) examined the effect of a highly palatable and caloric rich (" cafeteria ") diet on food-related cognition in rodents. Specifically, they used Pavlovian devaluation to determine if consumption of a cafeteria diet affects the ability to learn about food-related stimuli. Rats were trained to associate two cues with two distinct foods after which one of the foods was devalued via sensory-specific satiety, defined as a rejection of a food recently eaten to satiety while readily consuming another food with distinct sensory properties (Rolls, 1986). Rats fed a standard chow diet responded less during the stimulus that predicted the devalued food than during the stimulus that predicted the still valued food. In contrast, cafeteria-fed rats responded equally during both stimuli. Based on this result, the authors conclude that consumption of the cafeteria diet produces a deficit in the expression of stimulus-outcome learning and, in particular, of cue-food associations. However, in addition to the deficit observed in Pavlovian devaluation, the authors also reported that, following satiety-induced devaluation, cafeteria-fed rats failed to show sensory-specific satiety and consumed equal amounts of the devalued and valued foods. Indeed, following selective satiation, cafeteria-fed rats reduced their consumption of both the devalued and valued foods. As such, the authors have provided clear evidence that satiety-induced devaluation was not effective in selectively reducing the value of the prefed food in the cafeteria-fed rats. The reliance …