Previously, we have shown that satiety and metabolites increased after high-fat modified sham feeding (MSF). We assessed possible metabolic effects due to oral stimulation with a high-fat sham-fed ‘meal’, in comparison with a high-fat fed meal and with water, in the postprandial state. Fourteen healthy women (aged 18–40 years; BMI 22·5 (sd 3) kg/m2) were fed in energy balance during 4 d with a 50 % enegy as carbohydrate, 15 % energy as protein and 35 % energy as fat menu. On day 4, subjects were given one out of three test lunches, 5 h after a high-fat breakfast, in random order: a high-fat MSF lunch, water (W) or the same lunch to be eaten (E), during their 36 h stay in the respiration chamber, where substrate oxidation, 24 h energy expenditure (EE) and appetite profile were measured. Oral fat stimulation by MSF increased EE (W 6·3 (sd 0·8) v. MSF 6·9 (sd 1·0) kJ/min and E 6·8 (sd 0·7) kJ/min; P < 0·04) for 1 h, increased plasma insulin concentrations (t = 15; W 10·0 (sd 3·4) v. MSF 13·2 (sd 4·0) v. E 22·3 (sd 3·3) units/l; P < 0·0001), attenuated changes in plasma NEFA concentrations (t = 15, W 432 (sd 108) v. MSF 418 (sd 146) v. E 282 (sd 72) μmol/l; P < 0·0001), plasma TAG concentrations (t = 60; W 1092 (sd 548) v. MSF 1116 (sd 493) μmol/l and E 1350 (sd 352) μmol/l; P < 0·02) and plasma glycerol concentrations (t = 15, W 87 (sd 29) v. MSF 74 (sd 34) μmol/l and E 67 (sd 18) μmol/l; P < 0·03). Over a longer period of time, MSF had no effects on substrate oxidation, diet-induced thermogenesis or total EE. In addition to the previously observed metabolic effects of oral stimulation with fat, EE is stimulated up to 1 h after the MSF meal.

The present study was carried out to determine whether cephalic stimulation, associated with eating a meal, was sufficient stimulus to provoke the release of stored triacylglycerol (TAG) from a previous high-fat meal. Ten subjects were studied on three separate occasions. Following a 12 h overnight fast, subjects were given a standard mixed test meal which contained 56 g fat. Blood samples were taken before the meal and for 5 h after the meal when the subjects were randomly allocated to receive either water (control) or were modified sham fed a low-fat (6 g fat) or moderate-fat (38 g fat) meal. Blood samples were collected for a further 3 h. Compared with the control, modified sham feeding a low- or moderate-fat meal did not provoke an early entry of TAG, analysed in either plasma or TAG-rich lipoprotein (TRL) fraction (density <1.006 kg/l). The TRL-retinyl ester data showed similar findings. A cephalic phase secretion of pancreatic polypeptide, without a significant increase in cholecystokinin levels, was observed on modified sham feeding. Although these data indicate that modified sham feeding was carried out successfully, analysis of the fat content of the expectorant showed that our subjects may have accidentally ingested a small amount of fat (0.7 g for the low-fat meal and 2.4 g for the moderate-fat meal). Nevertheless, an early TAG peak following modified sham feeding was not demonstrated in the present study, suggesting that significant ingestion of food, and not just oro-sensory stimulation, is necessary to provoke the release of any TAG stored from a previous meal.