Unpredictability of access to a high fat/high sugar food can increase rats' intake

When food is readily available, human self-imposed restrictions on consumption of palatable foods can lead to binge eating. Rodent models of human bingeing have produced increased intakes. However, access to highly palatable foods in such models has been largely predictable. The aim of the present study was to examine whether unpredictability of access might increase intakes in an animal model of bingeing, one in which rats had unrestricted access to chow and water throughout. Stage 1 of Experiment 1 gave female rats 2-h access to Oreos on either an unpredictable schedule or daily. In Stage 2 both groups were switched to predictable access on alternate days to test for persistent elevated intakes in the Unpredictable group. Although Oreo consumption did not differ between the two groups in Stage 1, the Unpredictable group ate more Oreos in Stage 2. In Stage 1 of Experiment 2 both groups were given access to Oreos every two days on average. The Predictable group was given alternate day access at a fixed time of day, whereas access days and times could not be predicted by the Unpredictable group. The latter was found to eat more Oreos in Stage 1, but this difference between the groups did not persist in Stage 2. Unpredictability did not appear to impact body weight gain in the study. In conclusion, this study indicates that unpredictability can increase consumption of palatable foods in addition to the increase produced by intermittent access.