Effects of supplemental dietary fibre on subjective satiety in young healthy individuals: a randomised controlled trial

Abstract

Background: In the diets of people living in developed countries there is a deficit of dietary fibre, believed to be a contributing factor to obesity. Although foods containing wholegrains may be good sources of dietary fibre, such foods are lacking in many people’s diets due to preference or cost and an alternative means to increase fibre intake may be the addition of functional fibre into food. Such fibres have been investigated for their effect on satiety but research findings are ambiguous, potentially due to study design dissimilarities and small samples. Objective: To determine in two separate experiments whether the addition of 10g supplemental fibres, one gelling and one non-gelling, will increase satiety in healthy university students. To assess satiety using a novel food model as an alternative to the common method of visual analogue scales (VAS). Design: Two double-blind crossover trials were carried out with young healthy weight individuals, currently undertaking a university human nutrition paper. Participants fasted before attending two laboratories two weeks apart during which they consumed fibre-enriched bread on one occasion and a control bread on the other. The fibre-enriched breads contained either gelling FibreMaxTM (n=43) or non-gelling insoluble fruit-skin fibre (n=40). Subjective satiety was measure with nine VAS questions assessing; hunger, satisfaction, fullness, prospective intake, specific taste desires (sweet, savoury, salty, fatty) and thirst, along with an alternative novel measure, food models. These measures were undertaken at baseline and at 30 minute intervals post bread consumption for 180 minutes. Two different analyses were undertaken for the appetite VAS, AUC and slope gradients. Results: No significant differences for AUC of the VAS in both experiments. Fruit-skin fibre-enriched bread had ~216kJ less energy than the corresponding control, however an increased acute appetite sensation following its consumption was seen for satisfaction, fullness, prospective intake and combined appetite ratings of VAS (all P<0.05). Fruit-skin fibre-enriched bread also increased the desire for fatty foods after its consumption. There were no significant findings for FibreMaxTM –enriched bread on satiety. The food models revealed no differences in satiety between FibreMaxTM and fruit-skin fibre and their respective controls, however the prospective intake of sweet foods was shown by the food models to be unaffected regardless of which bread ingested. Conclusion: Addition of supplemental fibre did not influence overall satiety, specific taste desires or thirst. Although overall satiety remained unchanged the positive effect of fruit-skin fibre on lowering energy density was highlighted by the unaffected AUC of participant ratings and further by the greater acute appetite suppression. Food models presented a novel finding and appeared to have a greater sensitivity to the VAS, however further investigation of this measure is required. Moreover, the used of bread as a vehicle for supplemental fibre was successful in terms of practicality and realistic for incorporation into the diet of New Zealanders.