The effects of prolonged fibre exposure on microbiota gastro intestinal function and energy regulation

RATIONALE: Declining eating rate and emergence of fullness over a meal defines normal satiation. These changes are attenuated in the obese, hence slowing eating rate and amplifying fullness may be effective means of weight control, and might be achieved by manipulating food structure. Fibre supplements have been shown to reduce appetite through effects on post-prandial satiety, but may also have beneficial intra-meal actions. However, while some fibres can reduce energy intake, their precise effects on the development of fullness have seldom been tested; nor has there been systematic analysis of the mechanisms whereby any changes are induced. Due to their diverse physio-chemical properties and various bio-behavioural effects, fibres may be effective tools for the study of appetite processes, to advance the characterisation of the normal controls of hunger and satiety. Detailed study of fibre effects on eating and appetite, and exploitation of their individual properties may advance the development of novel weight control products. Fibres may affect a variety of factors to influence eating rate, fullness and energy intake. However, current data are limited in the range of fibres tested and by inconsistencies in method and findings. Research has focused on the effects of (often large quantities of) fibres on post-prandial satiety, with little emphasis on important intra-meal factors. APPROACH: As increased meal size (not meal frequency) is the most important component of over-consumption, modifications to food structure that specifically limit meal size may be more effective than manipulations that aim solely to reinforce inter-meal satiety. There is a clear need for more systematic analyses of fibre action, with standardised methodology, to identify fibres that can normalise eating rates and fullness when incorporated into foods - enabling individuals to establish healthier eating styles. The studentship examines fibre actions on the development of intra-meal satiation and the strength of post-meal satiety. The experiments will incorporate Universal Eating Monitor apparatus for continuous real-time measurement of eating. MATERIALS: The research will exploit the particular properties of different fibres (Resistant Starches and Fructo-oligosaccharides) to explore their appetite suppressant efficacy, and specific modes of action (in terms of behavioural, psychological, physiological and metabolic consequences). To achieve these aims, we will incorporate fibre as a meal ingredient and measure real time changes in satiation and satiety. This method will permit 1) the direct measures of the specific consequences of eating a meal; 2) identify fibres that most effectively reduce appetite, and 3) elucidated their temporal locus and mode of action through measures of specific biomarkers. These studies will have direct implications for both understanding the psychological/biological mediation of satiation and satiety, and the development of satisfying, filling foods that might aid weight loss by the prevention of over-consumption. OUTCOME: We will determine optimal appetite-suppressant doses of fibres, and assess their effects on: intake; intra-meal eating, sensory and appetite measures; post-meal satiety and compensatory intake; appetite-related gastrointestinal peptide activity (ghrelin, GIP, GLP-1 & PYY); specific markers for oro-caecal transit (C13/H2); blood glucose, insulin and FFA; and indices of colonic fermentation and gut microbiota modification. In addition to acute laboratory studies, we will assess the long-term (28 d) impact of fibre enrichment on each biomarker.