Impact of Beta-glucan Supplementation During Calorie and Carbohydrate-restricted Diet on Body Weight and Body Fat Loss, Appetite, and Gastrointestinal Appetite Hormones.

This study will investigate whether beta-glucan supplementation, when added to an energy and carbohydrate-restricted diet, facilitates body weight and body fat loss, and leads to less detrimental changes in subjective appetite and gastrointestinal appetite hormones. This will be a double-blind, randomised, controlled trial in which healthy females living with overweight and obesity will be randomly assigned to a beta-glucan or a cellulose (placebo) group (1:1 basis). The randomisation software will be used to generate a randomisation list. This list will be held by a person independent of the research team. During the 4-week intervention, participants will consume an energy and carbohydrate-restricted diet combined with 9 g/day of beta-glucan (beta-glucan group) or 9 g/day of cellulose (Placebo group). During the 4-week intervention, breakfasts and dinners will consist of energy-restricted meal replacements providing 200 kcal/ meal, while lunches will be low-carbohydrate meals providing 35% of habitual energy intake. Before and at the end of the intervention, participants will conduct an experimental trial, with pre- and post-intervention trials being identical. The experimental trials will take place in the metabolic room of the New Lister Building (NLB) of the Glasgow Royal Infirmary. During the experimental trials, body weight and body composition will be measured in the fasted state, and the collection of fasting and postprandial (for the duration of 240 minutes) blood samples will be conducted. For a meal, participants will consume the low-calorie breakfast, which will be a liquid meal replacement (Cambridge Weight Plan, Corby, UK), together with 3 g of beta-glucan. Subjective appetite scores will be measured in the fasted and postprandial states. To achieve total body water and thus body composition (fat mass and fat-free mass) measurements, saliva will be collected before and 3 and 3.5 hours after consumption of D2O (which will be consumed in the fasted state). For the duration of 24 hours before the experimental trial, participants will be asked to avoid coffee and alcohol. Participants will be required to record their food and drink intake for three days before the trial days of each experimental investigation.