Effects of amount and type of dietary fibre (soluble and insoluble) on short-term control of appetite.

Fibres which are soluble or insoluble in water have different physiochemical properties and may therefore be expected to exert different effects on post-ingestive satiety signals. This study compared the effects on short-term (24 h) appetite of two equienergetic high (22 g) fibre breakfasts, an equienergetic low fibre breakfast and a low energy, 'light' breakfast. Psyllium gum (the soluble fibre) and wheat bran (the insoluble fibre) were incorporated into breakfast cereals and consumed at breakfast by sixteen healthy, normal weight males after an overnight fast using a repeated measures, counterbalanced design. Ad libitum energy intake was assessed at a test snack 1.5 h after breakfast, later in the day using food boxes and the following day using food diaries. Motivation to eat and gastrointestinal sensations were tracked for the next 24 h. Hunger ratings showed a trend towards the subjects being less hungry and they consumed significantly less energy at snack time after the high insoluble than after the high soluble fibre breakfast cereal. The soluble fibre breakfast produced a greater suppression of snack intake than the light breakfast, but smaller suppression than the other breakfasts. Interestingly there was a trend toward reduced hunger and voluntary energy consumption following the soluble fibre compared with the insoluble fibre much later in the day (9.5-13.5 h after breakfast) although this was not significant. There was no significant effect of breakfast type on total day energy intake. The results suggest that different types of fibre modulate the timecourse of appetite control and may produce alterations in the experience of motivation and patterns of eating without necessarily effecting total energy intake.