Behavioral and physiological adaptations in rats during food-entrainment.

Food anticipatory activity (FAA) is the expression of a food entrained oscillator, which manifests under restricted feeding schedules (RFS). Food restriction to 2?h daily represents a metabolic challenge and requires behavioral and physiological adaptations in order to allow animals to ingest sufficient food for a 24?h cycle in a short 2?h interval. In order to characterize the behavioral and physiological adaptations during restricted feeding, rats were maintained for 3 weeks under a fixed RFS, an unpredictable RFS and ad libitum (AL) feeding conditions. Feeding behavior was recorded for 2?h during meal access for RFS groups and during the first 2?h of the dark period in AL controls. Body and stomach weight were also measured for the three feeding groups. There was a significant difference between restricted groups and AL controls in the latency and duration of feeding during the 2?h of food access. Restricted rats which could predict mealtime showed the shortest latency. In both RFS groups the stomach attained a large distension in contrast to AL controls, and total time spent in food ingestion was 3?–?4 fold higher than the AL. However, and despite these behavioral and physiological adaptations, restricted rats did not achieve a body weight gain at the end of the experiment, unlike the AL group. Present data indicate that during RFS rats develop behavioral and physiological adaptations to ingest increased amounts of food in a short interval. [ABSTRACT FROM AUTHOR]