No abstract

No abstract

Adaptation to a high fat diet is an important early stage in the pathogenesis of obesity [I]. It has been suggested previously [2,3] that subjects provided with artificial diets of varying fat content have shorter mouth to caecum transit times (MCTT) with increased dietary fat.The aim of this study was to examine whether there are changes in MCTT of a high fat meal during a period of consuming a diet containing an increased amount of fat. To reduce variability within the study, habitual food intake was manipulated to produce a high fat diet rather than the normal procedure of providing comparison between two artificial diets.With the approval of the local ethics committee (South Sheffield Ethics Committee, Royal Hallamshire Hospital, Sheffield), six healthy males volunteered for this study. Their physical characteristics (median (range)) were: age 27 (21-34), height 179 cm (170-189) and weight 69 kg (58.5-78.9) at the start of the test period. Subjects were chosen who were in general good health with no known history of gastro-intestinal pathology and who were not on any medication. Subjects were excluded if their Body Mass Index did not lie within a range of 19-25 kg/m'. Subjects were excluded if they consumed more than 35% of their total energy as fat above which subjects would be pre-adapted to a high fat diet as defined by Committee on Medical Aspects of Food Policy, 1994.Subjects recorded all food and drink consumed over a seven day period before MCTT of a high fat test meal (2840 kJ, 85 % fat by energy) was recorded. The test meal contained sufficient fibre (12 g) to allow for recording of MCTT by breath hydrogen analysis [4]. End expiratory breath samples were before and at 10 minute intervals after ingestion of the test meal. MCTT of the head of the test meal was taken as the time after ingestion at which there was a rise of 3 ppm above basal values which was maintained or increased over the next three consecutive 10 minute readings [5].For the subsequent three weeks, volunteers repeated the food diary. They also consumed high fat food sources to increase the content of fat in the diet. Subjects were provided with 125 ml of double cream and 50 g of roasted peanuts each day which increased the mean daily energy intake of 11 125 kJ (sem 457) (30 % fat (sem 1.4)) to a mean of 14960 kJ (46 % fat). The refined diet led to a mean increase of 1.1 kg (sem 0.1) in subjects' weights (p = 0.0085).During this period, MCTI' of the same test meal was measured at seven, fourteen and twenty-one days after the start of their high fat diet. Transit times measured at these weekly intervals and before the new diet were compared using repeated measures ANOVA. Significance was taken at 5%.There were significant differences between MCTT at the different stages of early adaptation to a high fat diet (p = 0.006) with MCTT significantly longer after three weeks of the new diet when compared with both before the start of the new diet (p = 0.027) and after just one week of the new regimen (p = 0.045) as shown in figure 1. There was ...

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

The physical progression of a meal along the gastrointestinal (GI) tract is controlled by the composition of the meal In particular, the presence of fat has been demonstrated to prolong stomach-tocaecum transit time in a dose-dependent manner [ I ] In addition, inhsing small amounts of fat directly into the ileum, results in slower GI transit of a test-meal (ileal break) Repetitive ifisions of fat into the ileum over a period of 5 weeks result in reduced sensitivity to fat, and normal (faster) transit of a test-meal [2]. Such adaptation to fat exposure may result in faster fat absorption. The present study investigates the time-course of transit adaptation by determining the effects of chronic feeding of high-fat diet for 9, 18 and 27 days on GI transit of low-fat and high-fat test-meals.Eighty-three male Sprague-Dawley rats were assigned to groups of equal mean body weight (3 18-3332. 11-6-8) and fed ad libitum either high-fat diet (HFD; 43% olive-oil wiw) or low-fat diet (LFD; 2 5% oil w/w). Body weight and food intake were recorded daily. GI transit was measured after 9, 18 and 27 days Rats were fasted for 18 hours and the transit of a 5 nil high-fat test meal (HFM, 70.30% liquidised washed baked-beans.olive oil) or a lowfat test meal (LFM, liquidised washed baked-beans, 1% oil) was tested. The meals were labelled with '"Tc-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 ten equal segments of the small intestine. Area-underthe-curve was calculated for each segment (31 and results are presented as percent of total counts for each traceThe body weight gains of the two dietary groups were similar after 9 and 18 days on the experimental diets After 27 days, animals fed high-fat diet were not significantly heavier than low-fat fed controls (Table 1) However, both these dietary groups show higher weight gains after 18 and 27 days when compared to naive controls, fed dry pellets from another study (data not shown). These data indicate that the differences in transit are not due to the weight gain observed in this model ofobesity, but to the differences in fat content of the rats' habitual diets Food intake determinations showed that animals fed the low-fat diet, compensated for the decreased energy density of the diet (0.7 MU100g) by increasing their food intake Rats fed the high-fat diet reduced their food intake, but not enough to compensate for the higher energy density ofthe high-fat diet (2. 2 MJ/IOOg).This resulted in higher average daily energy intake in the high-fat fed animals (476*3 1 kJ/rat/day) than in the low-fat fed group (203