Rapid gastric emptying (GE) and hence a shortened satiety period may contribute to the development of obesity. Cunningham et al. (Reference Cunningham, Daly and Horowitz1) were the first to establish in human subjects that feeding a high-fat (HF) diet for two weeks accelerates gastrointestinal (GI) transit. Since then, diets of only 3 d have been shown to reduce GE time(Reference Clegg, McKenna and McClean2). A 2-week HF-diet has also resulted in an increase in hunger during an oral fat tolerance test following the HF diet(Reference Boyd, O'Donovan and Doran3). Over longer periods than 2 weeks the effects of HF diets on GE and satiety is unknown. The aim of this study is to assess GI transit and satiety during and following a 4-week HF diet.
The study was a repeated measures design with ten male volunteers completing a 1-week HF diet intervention and seven completing a 1-week HF diet intervention with testing once a week on the same day throughout the 4 weeks. GE was measured using the 13C octanoic acid breath test and mouth to caecum transit time (MCTT) using the inulin H2 breath test. Satiety was analysed using visual analogue scales and an ad libitum buffet meal. Analysis was completed using repeated measures ANOVA. Statistical significance was set at P<0.05, data are expressed as mean (sd).
Body mass increased by 1.3 kg over the 4 weeks (P=0.036). GE latency time decreased over 1 week (45 (sd 8) v. 41 (sd 10) min; P=0.047) but there were no changes in any GE parameters over the 4 weeks. MCTT was accelerated after a 1 week HF diet (308 (sd 43) v. 248 (sd 83) min; P=0.036) but not after a 2–4 week HF diet. Satiety decreased over 1 week (P=0.01). Changes in satiety were also evident over the 4 weeks (Fig. 1a and b).
In conclusion, an HF diet affects GI transit and satiety over 1 week and satiety throughout 4 weeks on a HF diet. HF diet causes accelerations in GI transit that are temporary, which indicates a lesser role for dietary fat in the development of obesity.