This randomized crossover study investigates the effect of consuming a high-protein, high-fiber pre-fast meal on subjective satiety and glycemic responses during fasting hours in healthy adults. Participants will complete two dietary conditions in a randomized order: a standardized high-protein, high-fiber pre-fast meal and a low-protein, low-fiber pre-fast meal guided by dietary instructions. Each condition will be followed for two consecutive days and separated by a three-day washout period. Outcomes include subjective appetite sensations during fasting hours, glycemic profiles assessed using continuous glucose monitoring (CGM), and exploratory analyses examining the association between glucose dynamics and appetite sensations.

This study is a randomized crossover interventional trial conducted in healthy adults to evaluate the effect of a high-protein, high-fiber pre-fast meal on subjective satiety and glycemic responses during fasting hours.

Each participant will complete two study conditions in a randomized sequence: a high-protein, high-fiber pre-fast meal condition and a low-protein, low-fiber pre-fast meal condition. Each condition will be followed for two consecutive days and separated by a three-day washout period to minimize potential carryover effects.

During the high-protein, high-fiber condition, participants will consume a standardized pre-fast meal consisting of oats (40 g), Greek yogurt (160 g), peanut butter (16 g), dried cranberries (10 g), and almonds (6 g). Meals will be provided in pre-measured portions by the research team.

During the low-protein, low-fiber condition, participants will receive standardized written dietary instructions, including a list of foods to avoid, to guide consumption of a low-protein, low-fiber pre-fast meal. No calorie restriction will be applied in either study condition.

Subjective appetite sensations, including hunger, fullness, desire to eat, and prospective food consumption, will be assessed using visual analogue-type scales at predefined time points across the fasting day. Glycemic profiles will be continuously assessed using continuous glucose monitoring (CGM).

Exploratory analyses will examine temporal associations between CGM-derived glucose levels and glucose trends and subjective appetite sensations across the study day.

Inclusion Criteria:

• Adults aged 18 years and older
• Willingness to comply with study procedures, including fasting and continuous glucose monitoring
• Ability to provide informed consent

Exclusion Criteria:

• Diagnosed diabetes mellitus or known metabolic disease
• History of cardiovascular, gastrointestinal, or endocrine disorders that may affect study outcomes
• Use of medications known to affect glucose metabolism or appetite
• Pregnancy or lactation
• Known allergy or intolerance to any study meal components (oats, dairy, peanuts, nuts, cranberries)

De-identified individual participant data (IPD) collected in this study will not be made publicly available. Data will be used for research purposes by the study investigators only