The Satiety Control Optimization by Nutritional Enhancement Study

High-glycaemic foods contribute to elevated risk of obesity, type 2 diabetes, and cardiometabolic disease. Replacing digestible carbohydrates with dietary fibres is known to reduce postprandial glycaemic excursions, enhance satiety, and support beneficial microbial fermentation. However, limited evidence exists on how interactions between different isolated fibres within a processed food matrix may modulate these responses, particularly when such interactions could recreate structural features of intrinsic plant fibre networks that naturally restrict starch accessibility and alter fermentation dynamics. This randomized, single-blinded, placebo-controlled crossover trial will investigate how isolated dietary fibres, alone and in combination, influence metabolic and microbial responses when incorporated into a commonly consumed cereal-based food (scone). Overweight but otherwise healthy adults (BMI 25-\<30 kg/m²) will consume seven fibre-enriched scone formulations across two consecutive mornings per intervention phase. Outcomes include postprandial glycaemic response measured via continuous glucose monitoring (primary outcome), perceived satiety and energy intake, gastrointestinal symptoms, fermentation dynamics via breath hydrogen and methane, and gut microbiota composition assessed through 16S rRNA sequencing. This study will generate novel insights into potential synergistic interactions between isolated fibres within a food matrix and their consequences for glycaemic control, satiety, microbial fermentation, and community. Findings will inform next-generation food design strategies aimed at replicating complex intrinsic fibre structures to enhance the health impact of processed foods.

The study will be conducted over a 28-day period, during which each participant will complete a structured sequence of controlled dietary interventions while continuous metabolic and gastrointestinal data are collected. Participants will rotate through seven intervention phases, each lasting two consecutive days. In each phase, they will consume one of the fibre-enriched scone formulations provided by the research team, accompanied by standardized, calorie-controlled meals. Snacks will be provided but may be consumed ad libitum, ensuring consistent macronutrient intake across intervention days while preserving ecological validity. To maintain data quality and support participant adherence, each intervention phase is followed by a washout day during which participants return to their habitual diet. These washout periods minimize carryover effects from previous fibre exposures and allow both glycaemic responses and microbial activity to stabilize before the next intervention. Weekends are intentionally left free of study foods and structured routines, a design choice that improves flexibility, reduces participant fatigue, and helps maintain high compliance without compromising continuous data collection. Upon enrolment, participants will receive two continuous glucose monitoring (CGM) sensors, each worn for 14 days, ensuring uninterrupted interstitial glucose measurement throughout the study. This approach allows precise characterization of postprandial glycaemic responses to each test food under free-living conditions while minimizing participant burden. To assess fermentation dynamics, participants will provide breath samples using a portable breath-analysis device capable of quantifying hydrogen and methane. Measurements will be collected immediately before and after each intervention meal, enabling assessment of both the magnitude and timing of microbial fermentation in response to the different fibre combinations. Gastrointestinal sensations and tolerance will be evaluated using validated questionnaires that capture bloating, discomfort, stool frequency, and form (including the Bristol Stool Scale), and other relevant symptoms. Satiety and hunger perception will be assessed using standardized visual analogue scales administered before and after each intervention meal, providing detailed insight into subjective digestive and appetite-related responses. Eligible participants are healthy men and women aged 18-45 years with a body mass index between 25 and \<30 kg/m². All participants must be weight-stable for at least three months prior to enrolment and free from metabolic, gastrointestinal, or chronic inflammatory diseases. Exclusion criteria include diagnosed diabetes or pre-diabetes, use of glucose-modulating or lipid-lowering medications, recent antibiotic therapy, adherence to restrictive diets (such as ketogenic, vegan, or medically prescribed regimens), significant food allergies relevant to study products, smoking, pregnancy or breastfeeding, and any condition that may interfere with digestion, absorption, or gut microbiota composition. Overall, the combination of controlled feeding, continuous glucose monitoring, breath-based fermentation measurements, validated gastrointestinal and satiety assessments, and microbiome profiling will generate a comprehensive dataset describing how isolated dietary fibres shape metabolic, digestive, and microbial responses when incorporated into a familiar cereal-based food matrix.