Effects of varying the inter-meal interval on relationships between antral area, gut hormones and energy intake following a nutrient drink in healthy lean humans.

The aim of this study was to determine: (i) the effects of varying the inter-meal interval on subsequent energy intake, and (ii) temporal relationships between postprandial changes in antral area and gastrointestinal hormone concentrations with energy intake. 16 healthy lean participants (10 M, 6 F) were studied on 4 occasions in randomized fashion. Participants consumed 500ml of water 180min ("control"), or 500ml of a mixed-nutrient drink (750kcal) 30 ("EI-30"), 90 ("EI-90") or 180 ("EI-180") min, prior to a cold, buffet-style meal, from which energy intake was quantified. Antral area was measured using 2D-ultrasound, perceptions of hunger and fullness were scored using visual analogue scales, and blood samples collected at regular intervals for analysis of plasma cholecystokinin (CCK), peptide YY (PYY) and ghrelin concentrations. All nutrient drinks increased antral area, stimulated CCK and PYY, and suppressed ghrelin and energy intake (EI-30: -367±69, EI-90: -291±69, EI-180: -219±72kcal, P<0.05, for all), compared with control. Energy intake was related directly to the length of the inter-meal interval (R=0.33, P<0.01), such that as the inter-meal interval increased, energy intake increased. There was a strong relationship between antral area (R=-0.76, P<0.001), and weaker relationships between CCK (R=-0.36, P<0.01) and PYY (R=-0.34, P<0.01), with the inter-meal interval. In conclusion, energy intake increased as the inter-meal interval increased. This was associated with temporal changes in gastric content (antral area) and plasma gut hormone concentrations.