Background: Human obesity is strongly linked to high-fat diet (HFD) consumption. Evidence from animal studies shows an attenuation of the appetite suppressive effects of fat following a HFD, and in modelled obesity. Gastrointestinal (GI) responses to fat in obese humans are inconsistently reported, potentially due to differences in habitual fat and energy intake (EI) of study participants. Here, we compared the effects of intraduodenal (ID) fat infusion on pyloric motility (an important determinant of EI) and subsequent ad libitum EI in lean, overweight and obese humans, and examined relationships with habitual dietary fat and EI.
Methods: The effects of ID fat infusion (2 kcal/min for 120 min) on isolated pyloric pressure waves (IPPWs) were assessed in fasted lean (L: BMI: 21.5 ± 0.5 kg.m2, n = 18), overweight (OW: BMI: 26.8 ± 0.4 kg.m2, n = 13) and obese (OB: BMI: 34.2 ± 1.5 kg.m2, n=9) healthy volunteers. Ad libitum EI (buffet lunch) was quantified immediately thereafter. Habitual dietary fat and EIs were assessed using 3 x 24-hour recall diaries. Data are presented as mean ± SEM.
Results: Habitual EI (kJ) (L: 8740 ± 784; OW: 8372 ± 538; OB: 8387 ± 1241) and the percentage of energy consumed as fat (L: 34 ± 2; OW: 32 ± 2; OB: 35 ± 2) did not significantly differ between study groups. ID fat increased IPPWs (L: 81.7 ± 38.4 mmHg; OW: 79.8 ± 23.2 mmHg; OB: 151.1 ± 40.4), with no statistical difference between groups. There was also no difference in EI (kJ) (L: 4342 ± 415; OW: 4534 ± 458; OB: 4382 ± 514) or fat consumption at the buffet meal.