Gastrointestinal transit adaptation to low- and high-fat cafeteria diets

Abstract

Cafeteria diets (CD) have been commonly used as a model of obesity in the rat. These diets typically consist of several different high-fat supermarket foods, presented in a rotating order, to maintain the 'novelty' stimulus to eating Cafeteria diets are reported to lead to increased food and energy consumption and increased weight gain. Dameto and colleagues (1991) have shown that feeding a high-fat CD to weaning rats leads to obesity and accelerated transit of an inert meal through the gastrointestinal tract (GI) [I]. The aim of the present study was to investigate the eating behaviour and GI transit of adult rats, fed either a low-fat CD or a high-fat CD.Twenty-one male Sprague-Dawley rats were assigned to three groups of equal mean body weight (2 1 1-2 14g; n=7) and fed ad libitum either low-fat CD (LFCD), high-fat CD (HFCD) or pellet control (CTRL). The LFCD consisted of potatoes, bananas, carrots, shredded wheat, bread and liver. HFCD consisted of chips, Madeira cake, smoked fish, biscuits, kit-kat and pop-corn. The composition of these diets is shown in table 1 For each diet four different items were presented daily with rat pellets Body weight and the consumption of individual food items were recorded daily and food intake data were corrected for evaporation. GI transit was measured after 35 days. Rats were fasted for 18 hours and the transit of a 5 ml high-fat test meal (HFM; 80 20% liquidised washed baked-beans:olive oil w/w) was tested. The meal was labelled with 99Tc-Tin colloid and rats were killed by chloroform inhalation four hours after intubation. The activity along the excised gut was recorded using a gamma-counter and computer. The recorded trace was divided into stomach, caecum and three equal segments of the small intestine (proxmial, middle and distal). Area-under-the-curve was calculated for each segment [2] and results are presented as percent of total counts for each trace. compensated for the decreased energy density of their diet by increasing their food intake (Table 1) This over-eating resulted in increased total energy intake compared to the CTRL group (p<O.OI). Rats fed HFCD significantly reduced their food intake in grams, but not enough to compensate for the higher energy density of their diet. The reduction in food intake resulted in higher average daily energy intake in the animals fed HFCD than the other two groups (p<O.OI). However, these differences in energy intake and fat intake did not result in significant changes in body weight, as body weight gains of the three dietary groups were not significantly different (Table 1). Both LFCD and HFCD fed rats selected food items and amounts, such that their average fat intake was lower than that ofthe available diet. The differences between the presented average fat content and actual consumption demonstrates the need to record individual food items intake for the accurate determination of nutrient intake Table 1.