Wheat dextrin soluble fibre may have metabolic and health benefits, potentially acting via mechanisms governed by the selective modulation of the human gut microbiota. Our aim was to examine the impact of wheat dextrin on the composition and metabolic activity of the gut microbiota. We used a validated in vitro three-stage continuous culture human colonic model (gut model) system comprised of vessels simulating anatomical regions of the human colon. To mimic human ingestion, 7 g of wheat dextrin (NUTRIOSE® FB06) was administered to three gut models, twice daily at 10.00 and 15.00, for a total of 18 days. Samples were collected and analysed for microbial composition and organic acid concentrations by 16S rRNA-based fluorescence in situ hybridisation and gas chromatography approaches, respectively. Wheat dextrin mediated a significant increase in total bacteria in vessels simulating the transverse and distal colon, and a significant increase in key butyrate-producing bacteria Clostridium cluster XIVa and Roseburia genus in all vessels of the gut model. The production of principal short-chain fatty acids, acetate, propionate and butyrate, which have been purported to have protective, trophic and metabolic host benefits, were increased. Specifically, wheat dextrin fermentation had a significant butyrogenic effect in all vessels of the gut model and significantly increased production of acetate (vessels 2 and 3) and propionate (vessel 3), simulating the transverse and distal regions of the human colon, respectively. In conclusion, wheat dextrin NUTRIOSE® FB06 is selectively fermented in vitro by Clostridium cluster XIVa and Roseburia genus and beneficially alters the metabolic profile of the human gut microbiota.

Alterations in the composition and metabolic activity of the gut microbiota appear to contribute to the development of obesity and associated metabolic diseases. However, the extent of this relationship remains unknown. Modulating the gut microbiota with non-digestible carbohydrates (NDC) may exert anti-obesogenic effects through various metabolic pathways including changes to appetite regulation, glucose and lipid metabolism and inflammation. The NDC vary in physicochemical structure and this may govern their physical properties and fermentation by specific gut bacterial populations. Much research in this area has focused on established prebiotics, especially fructans (i.e. inulin and fructo-oligosaccharides); however, there is increasing interest in the metabolic effects of other NDC, such as resistant dextrin. Data presented in this review provide evidence from mechanistic and intervention studies that certain fermentable NDC, including resistant dextrin, are able to modulate the gut microbiota and may alter metabolic process associated with obesity, including appetite regulation, energy and lipid metabolism and inflammation. To confirm these effects and elucidate the responsible mechanisms, further well-controlled human intervention studies are required to investigate the impact of NDC on the composition and function of the gut microbiota and at the same time determine concomitant effects on host metabolism and physiology. (1) . In the UK population, it is estimated that 26 % of boys, 25 % of girls, 67 % of men and 57 % of women are currently overweight or obese (1) . Characterised by the accumulation of excess body fat, overweight and obesity are associated with a chronic low-grade systemic inflammation and other adverse metabolic effects. Consequently, the risk of pathologies including CVD, type 2 diabetes mellitus, chronic obstructive pulmonary disease, colon cancer, breast cancer, osteoarthritis, liver and gall bladder disease and reproductive dysfunction, are increased (2) . Overweight and obesity are also thought to increase the risk of common cognitive issues, such as anxiety and depression (3) . Population-based interventions to reduce the prevalence of overweight and obesity are now implemented as part of wider public health strategies in the majority of developed countries worldwide. In the UK, the Department of Health aims to achieve, by 2020, a sustained downward trend in the level of excess weight in children and a downward trend in the level of excess weight averaged across all adults (4) . Such interventions focus primarily on encouraging healthier food choices and increasing physical activity; however, they must compete with the *Corresponding author: M. R. Hobden, email M.R.Hobden@reading.ac.uk Abbreviations: AXOS, arabinoxylan-oligosaccharides; FFAR, free-fatty acid receptor; GLP-1, glucagon-like peptide-1; FOS, fructooligosaccharides; NDC, non-digestible carbohydrate; PYY, peptide YY.

BackgroundPreload studies are used to investigate the satiating effects of foods and food ingredients. However, the design of preload studies is complex, with many methodological considerations influencing appetite responses. The aim of this pilot investigation was to determine acceptability, and optimise methods, for a future satiety preload study. Specifically, we investigated the effects of altering (i) energy intake at a standardised breakfast (gender-specific or non-gender specific), and (ii) the duration between mid-morning preload and ad libitum lunch meal, on morning appetite scores and energy intake at lunch.MethodsParticipants attended a single study visit. Female participants consumed a 214-kcal breakfast (n = 10) or 266-kcal breakfast (n = 10), equivalent to 10% of recommended daily energy intakes for females and males, respectively. Male participants (n = 20) consumed a 266-kcal breakfast. All participants received a 250-ml orange juice preload 2 h after breakfast. The impact of different study timings was evaluated in male participants, with 10 males following one protocol (protocol 1) and 10 males following another (protocol 2). The duration between preload and ad libitum lunch meal was 2 h (protocol 1) or 2.5 h (protocol 2), with the ad libitum lunch meal provided at 12.00 or 13.00, respectively. All female participants followed protocol 2. Visual analogue scale (VAS) questionnaires were used to assess appetite responses and food/drink palatability.ResultsCorrelation between male and female appetite scores was higher with the provision of a gender-specific breakfast, compared to non-gender-specific breakfast (Pearson correlation of 0.747 and 0.479, respectively). No differences in subjective appetite or ad libitum energy intake were found between protocols 1 and 2. VAS mean ratings of liking, enjoyment, and palatability were all > 66 out of 100 mm for breakfast, preload, and lunch meals.ConclusionsThe findings of this pilot study confirm the acceptability of this methodology for future satiety preload studies. Appetite scores increased from preload to ad libitum lunch meal; however, no specific differences were found between protocols. The results highlight the importance of considering energy intake prior to preload provision, with a gender-specific breakfast improving the correlation between male and female appetite score responses to a morning preload.

Purpose Resistant dextrin (RD) supplementation has been shown to alter satiety, glycaemia, and body weight, in overweight Chinese men; however, there are limited data on its effects in other demographic groups. Here, we investigated the effects of RD on satiety in healthy adults living in the United Kingdom. Methods 20 normal weight and 16 overweight adults completed this randomised controlled cross-over study. Either RD (14 g/day NUTRIOSE® FB06) or maltodextrin control was consumed in mid-morning and mid-afternoon preload beverages over a 28-day treatment period with crossover after a 28-day washout. During 10-h study visits (on days 1, 14, and 28 of each treatment period), satietogenic, glycaemic and anorectic hormonal responses to provided meals were assessed. Results Chronic supplementation with RD was associated with higher fasted satiety scores at day 14 (P = 0.006) and day 28 (P = 0.040), compared to control. RD also increased satiety after the mid-morning intervention drink, but it was associated with a reduction in post-meal satiety following both the lunch and evening meals (P < 0.01). The glycaemic response to the mid-morning intervention drink (0–30 min) was attenuated following RD supplementation (P < 0.01). Whilst not a primary endpoint we also observed lower systolic blood pressure at day 14 (P = 0.035) and 28 (P = 0.030), compared to day 1, following RD supplementation in the normal weight group. Energy intake and anthropometrics were unaffected. Conclusions RD supplementation modified satiety and glycaemic responses in this cohort, further studies are required to determine longer-term effects on body weight control and metabolic markers. Clinicaltrials.gov registration CT02041975 (22/01/2014)

Laboratory-based pre-load studies are often used to quantify the effects of foods and/or food ingredients on satiety and satiation. Important considerations when designing pre-load studies include, but are not limited to, the timings of the study meals in relation to habitual intake, the duration between the pre-load and ad libitum test meal, and the nutrient content and palatability of the study meals provided (1) . We conducted a pilot study to determine the satiety effects of, i) a gender-specific compared to a non gender-specific breakfast meal, and ii) the duration between pre-load and lunch (test meal), and the time of lunch provision. The palatability of the study meals and pre-load were also evaluated.Forty healthy adult volunteers, with a BMI between 22·0 and 27·9 kg/m 2 , attended a single study visit at the Hugh Sinclair Unit of Human Nutrition, University of Reading. Male volunteers (n = 20) received a 265·8 kcal breakfast meal, equivalent to ∼10 % of the population estimated average daily energy requirement for males (2) . Female volunteers received either the same 265·8 kcal breakfast (n = 10) or a lower energy, female-specific, breakfast of 213·9 kcal (n = 10), equivalent to ∼10 % of the population estimated average daily energy requirement for females (2) . A 200 ml orange juice pre-load was consumed 2 h after breakfast. Ten male volunteers followed protocol 1 (lunch provided at 12·00, 2 h after the pre-load) and thirty volunteers (male n = 10, female n = 20) followed protocol 2 (lunch provided at 13·00, 2·5 h after the pre-load). Lunch was a pasta-based, single-course, meal provided ad libitum. Visual analogue scales (VAS) were completed at regular intervals throughout the study visit to assess subjective satiety and the palatability of the study meals and preload.AUC satiety scores before lunch were 3·4 ± 2·2 mm × 15 min (mean ± SD) for protocol 1 and 4·5 ± 1·7 mm × 15 min for protocol 2, however this was not found to be significantly different following analysis using one-way ANOVA. Pearson correlations revealed that the pre-load to lunch satiety scores of the male volunteers following protocol 2 were more strongly correlated with the satiety scores of the female volunteers following protocol 2 with gender-specific breakfast (r = 0·51), compared to non gender-specific breakfast (r = 0·41). As expected, male volunteers consumed significantly more energy at lunch than the female volunteers (P < 0·05). No significant differences were found between protocol 1 and protocol 2 for ad libitum energy intake at lunch. Additionally, no significant differences were found for energy intake at lunch between the female volunteers that consumed the gender-specific compared to non gender-specific breakfast. Mean scores for palatability, enjoyment, and taste of the breakfast, pre-load and lunch meals were all above 65 (out of 100) and did not differ between the study groups.In conclusion, a gender-specific breakfast meal was found to improve the correlation between male and female volunteers for satiety measure...