Rapid gastric emptying and hence a shortened satiety period may contribute to the development of obesity (1). Feeding a high-fat diet for 14 days has been found to accelerate gastric emptying (GE) and mouth to caecum transit time (MCTT) (2). The aim of the current study was to examine the effect of a three-day high-fat diet on gastrointestinal transit and satiety. Eleven healthy male volunteers were recruited (age 24.7±3.1yrs; height 181.5±7.9cm; weight 81.8±9.1kg; all data mean±S.D.) and undertook three stages: (i) they recorded their diet for a three-day period (PRE), (ii) they repeated their diet plus either a yoghurt supplement (LFY), or a yoghurt and oil supplement (HFY), given in randomised order, and (iii) they repeated their diet plus the alternate supplement. Each three days diet was followed by a test day. On each test day volunteers arrived in the laboratory following a 12-hour overnight fast. They consumed a high-fat pancake breakfast (61% energy from fat). Breath samples were collected for the following six hours and volunteers were asked to rate their satiety using a visual analogue scale (VAS) every 30-minutes. GE was measured using the 13C-octanoic acid breath test (3), and MCTT using the breath H2 technique (4). Volunteers were allowed to eat ad libitum for the rest of the day weighing and recording the food consumed. Data were tested for significance (p<0.05) using repeated measures analysis of variance (ANOVA). During the intervention volunteers’ daily average fat intake increased from 89.5±14.7g (PRE) to 97.5±15.6g (LFY) to 187.3±15.4g (HFY), and their energy intake from 11.06±1.73MJ (PRE) to 11.99±1.96MJ (LFY) to 15.45±1.74MJ (HFY) (p0.05) (n=5). Following all meals volunteers became less satiated over the six-hour period; hunger (p=0.005), desire to eat (p=0.003), and fullness (p=0.002) (n=11). However, results from the VAS showed no difference between the three diets for any of the satiety parameters. There were no significant differences in energy or macronutrient dietary intakes on the day of each test session (n=11). Results suggest that alteration in gastrointestinal transit following a high-fat diet may begin in the intestine, and may develop after a longer intervention such as two weeks to accelerating stomach emptying as reported by Cunningham et al. (1991). The lack of changes in GE rates after a three-day high-fat diet may explain why satiety is not altered by the high-fat diet.