Energy density in cafeteria diet induced hyperphagia in the rat.

Rats that are fed cafeteria diet (CD) are a widely used model of obesity. Presenting a varied and energy-dense diet often leads to hyperphagia and weight gain. However, the exact macronutrient composition of ingested food remains difficult to measure accurately. The current investigation aims to improve the accuracy of food intake calculations using a novel compensation for water evaporation, and to examine the role of energy density in CD-induced hyperphagia. Seven rats were presented daily with four foods, on rotation from a list of 36 different items, for a period of 43 days and compared to chow-fed controls (n=6). Correcting for evaporation corrected an overestimation by 8% of energy intake in rats fed CD. Rats consumed 25% more food by weight when fed CD as compared to controls. Similar to human studies, exposure to CD resulted in a 58% increase in energy intake. Energy density was positively correlated with energy intake in rats fed CD. Body weight gain was significantly elevated from day 20 onwards, suggesting the onset of obesity. This study removes evaporation bias from measurements of food intake in CD and supports the conclusion that a varied, energetically dense diet induces hyperphagia and obesity in the rat.