Circadian Rhythm, Meal Timing, Medical Residents, Nutrition Intake, Sleep Quality
Conditions
Brief summary
This randomized controlled trial aims to evaluate the effects of last meal composition and timing on sleep quality and circadian gene expression among medical residents in Jordanian hospitals. Sleep disturbances are common in this population due to long working hours, high stress, and irregular eating schedules. Chrono-nutrition, the science of aligning food intake with circadian rhythms, may provide a practical approach to improving sleep and overall well-being. Participants will be randomly assigned to one of three groups: 1. High-carbohydrate last meal (≈80% of dinner calories from carbohydrates), 2. High-protein last meal (≈40-50% of dinner calories from protein), 3. Control group consuming a balanced standard meal. Each participant will consume the assigned meal 3-4 hours before bedtime for two weeks. Sleep quality will be measured using the Pittsburgh Sleep Quality Index (PSQI) and smartwatch-derived parameters, while salivary samples collected pre- and post-intervention will be analyzed for CLOCK and BMAL1 gene expression. The study will also include dietary, anthropometric, and physical activity assessments. This study has been approved by the Institutional Review Board of the University of Jordan (IRB No. 491/2025). Recruitment has not yet started. Enrollment is expected to begin in December 2025, with primary data collection completed by June 2026 and final study completion by December 2026.
Interventions
DIETARY_SUPPLEMENTHigh-Carbohydrate Last Meal
Dinner ≈30% daily kcal; \ 80% carb; taken 3-4 h before sleep for 2 weeks
DIETARY_SUPPLEMENTHigh-Protein Last Meal
Dinner ≈30% daily kcal; \ 38-54% protein; 3-4 h before sleep for 2 weeks.
DIETARY_SUPPLEMENTBalanced Standard Dinner
Standard macronutrient distribution; same timing (3-4h pre-sleep) and 2-week duration.
Sponsors
University of Jordan
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
25 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Currently enrolled and working in Jordanian hospitals. * Not currently following a specific diet or weight-loss program. * Willing to comply with study protocol and intervention meals for two weeks. Provide written informed consent before participation.
Exclusion criteria
* Presence of any chronic medical condition (e.g., diabetes, thyroid disorders, gastrointestinal, cardiovascular, or respiratory diseases). * Diagnosed sleep disorders, such as insomnia, sleep apnea, or restless legs syndrome. * Mental health disorders (stress, anxiety, or depression diagnosed or medicated). * Pregnancy or lactation. * Use of medications or herbal supplements known to affect sleep (e.g., melatonin, chamomile, ashwagandha, lavender). * Caffeine dependence exceeding moderate levels ( \>400 mg caffeine/day).
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Sleep Quality (PSQI Global Score) | Baseline and 2 weeks post-intervention | Sleep quality will be assessed using the Pittsburgh Sleep Quality Index (PSQI) before and after the 2-week intervention. The PSQI total score (0-21) will quantify subjective sleep quality; higher scores indicate poorer sleep |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in BMAL-1 Gene Expression | Baseline and 2 weeks post-intervention | BMAL-1 mRNA levels will be analyzed in the same saliva samples via real-time PCR. Changes will be compared across meal groups. |
| Change in Total Sleep Duration | 1 week baseline and 2 weeks during intervention | Total sleep duration will be objectively measured using smartwatch data and expressed as average nightly sleep duration. Unit of Measure: Minutes per night |
| Change in CLOCK Gene Expression | Baseline and 2 weeks post-intervention | CLOCK mRNA expression will be measured in salivary samples collected pre- and post-intervention using RT-PCR. Relative quantification (ΔCt method) will determine expression changes. |
| Change in Sleep Stage Distribution | 1 week baseline and 2 weeks during intervention | Sleep stage distribution (light, deep, and REM sleep) will be assessed using smartwatch data and expressed as percentage of total sleep time. Unit of Measure: Percentage (%) |
| Change in Average Heart Rate During Sleep | 1 week baseline and 2 weeks during intervention | Average heart rate during sleep will be measured using smartwatch data. Unit of Measure: Beats per minute (bpm) |
| Change in Sleep Efficiency | 1 week baseline and 2 weeks during intervention | Sleep efficiency will be calculated as the percentage of total sleep time divided by time in bed using smartwatch data. Unit of Measure: Percentage (%) |
Countries
Jordan
Outcome results
None listed