Bread remains one of the most widely consumed staple foods worldwide, with wheat flour serving as its traditional foundation. However, the widespread dependence on refined wheat-based bread has paralleled the rising prevalence of type 2 diabetes (T2D), partly owing to its high glycaemic index (GI), which results in rapid increases in blood glucose levels. Enhancing the nutritional quality of bread, therefore, represents an important target for dietary intervention.

Developing alternative flour blends for bread production presents a potential strategy for improving glycaemic control and supporting glucose homeostasis. Accordingly, this clinical trial aims to determine whether the partial replacement of wheat flour with legume flours, including chickpea, pea, and lentil, in Arabic bread formulations can lower glycaemic responses compared with traditional Arabic wheat bread.

This study will be a crossover trial. Participants living with overweight and obesity will be recruited and fully informed about the study before giving informed consent. Eligible participants will attend the University of Nottingham on 4 separate visits following an overnight fast of at least 10 hours. On each visit, participants will consume one of three Arabic bread formulations or a control, with a one-week washout between visits. Each bread sample will provide an equivalent of 50 g of available carbohydrate:

1. Control bread (100% wheat flour)
2. Arabic bread containing 30% chickpea flour, with 70% wheat flour (primary comparison with control)
3. Arabic bread containing 30% pea flour, with 70% wheat flour(optional secondary comparison with control)
4. Arabic bread containing 30% lentil flour, with 70% wheat flour (optional secondary comparison with control)

The primary focus of this study is the comparison between the control bread and the chickpea-enriched bread, as chickpea flour represents the main intervention. The pea-enriched bread and lentil-enriched variants are included as optional secondary comparisons to provide additional insights into the broader effect of legume flour substitution on glycaemic response.

Study Visits:

The procedures for each visit are summarised below:

1. Pre-visit fast: Participants will fast for at least 10 hours before each visit.
2. Blood glucose sampling: Capillary blood glucose will be measured via finger prick at baseline and at regular intervals over 120 minutes following consumption (0, 15, 30, 60, 90, and 120 min) of the bread sample to assess the postprandial glycaemic response.
3. Appetite assessment: Participants will complete visual analogue scale questionnaires at baseline and at set intervals throughout each visit to assess subjective appetite responses.
4. Sensory evaluation: Participants will be asked to rate the sensory acceptability of each bread sample using a 9-point hedonic scale immediately after consumption.
5. Dietary intake: Participants will complete 24-hour food diaries in each visit.

Gastrointestinal symptoms will also be monitored via a brief self-reported questionnaire at baseline and post-consumption.

Inclusion Criteria:

• Participants will be adults living with overweight or obesity (Body Mass Index [BMI] > 25 kg/m²).
• Participants will be of any gender.
• Participants will be aged 18 to 65.
• Participants will be from any sociodemographic background.
• Participants will be able to provide informed consent.
• Participants will be able to understand spoken and written English and be able to record their responses to questionnaires.

Exclusion Criteria:

• Those with food allergies or intolerances to any of the study ingredients, including wheat, chickpeas, lentils, or peas, will not be eligible.
• Individuals with a known diagnosis of metabolic or chronic health conditions, such as diabetes, insulin resistance, hypertension, or phenylketonuria, will be excluded due to the potential impact on glycaemic control and study outcomes.
• Participants with a fasting blood glucose level of above 7.0 mmol/L.
• Use of medications that influence blood glucose levels (e.g., corticosteroids, antipsychotics, antiviral protease inhibitors) or substances that interfere with digestion and absorption (such as laxatives or fibre supplements) will result in exclusion.
• Pregnant or breastfeeding individuals will not be included due to the physiological changes that may influence study outcomes.
• Participants with implanted medical devices, including pacemakers, artificial organs, defibrillators, or joint replacements, will be excluded for safety considerations.
• Anyone who has undergone major surgery or hospitalisation within the last 5 months will be deemed ineligible.
• Individuals who have participated in another research study involving invasive procedures within the last 3 months will be excluded.

Participants will be masked to the type of bread they are consuming at each visit.