This randomized controlled trial will evaluate the impact of chrono-nutrition, a dietary approach that aligns meal timing with the body's circadian rhythms, on weight change, metabolic outcomes, appetite, and gut microbiota in post-bariatric surgery patients. A total of 246 adults who underwent sleeve gastrectomy at least six months earlier will be enrolled at King Saud Medical City. Participants will be randomized to receive either standard post-bariatric nutritional care or personalized chrono-nutrition based on individual chronotype. Outcomes include weight change, metabolic biomarkers, dietary behaviors, sleep patterns, and gut microbiota composition. The study aims to determine whether integrating chrono-nutrition into post-bariatric follow-up can enhance metabolic health and improve long-term health.
Adults aged 18-50 years who underwent Sleeve Gastrectomy (SG) 6 Months prior to enrollment.
Have achieved ≥50% of excess weight loss post-surgery (to ensure initial success).
Current BMI between 25-40 kg/m².
No major postoperative complications and cleared for a regular diet by their healthcare provider.
• Pregnancy or planned pregnancy during the study period, and post menopaused females
Current diagnosis of severe psychiatric illness that may interfere with adherence (e.g., untreated major depression, psychosis, severe eating disorders).
Active malignancy or serious chronic disease unrelated to obesity that may confound outcomes (e.g., advanced renal failure, uncontrolled liver disease).
Use of medications known to significantly alter circadian rhythm or metabolism (e.g., corticosteroids, melatonin therapy) within the last 3 months.
Parallel
Standard Post-Bariatric Care (Control)
BehavioralParticipants receive routine post-bariatric nutritional care with no prescribed meal-timing window. Dietitians provide standard guidance on protein adequacy (\~60-80 g/day unless otherwise indicated), hydration, and routine micronutrient supplementation per clinic practice. Follow-ups occur at 3, 6, and 12 months; outcomes include body weight, metabolic markers, appetite-related hormones, questionnaires, wearables, and stool samples. This arm controls for the effects of usual care and non-timing dietary counseling.
Early Time-Restricted Eating (eTRE)
BehavioralParticipants consume all caloric intake within a fixed daytime 10-hour window (08:00-18:00) on ≥6 days/week. Water/unsweetened tea/black coffee are allowed outside the window. Diet composition follows bariatric guidelines (protein \~60-80 g/day, hydration, routine micronutrients). Dietitians provide structured meal-timing plans and problem-solving support; timing logs and wearables document adherence. Assessments at 3, 6, and 12 months mirror the control arm.
Chronotype-Based Chrono-Nutrition (CB-CN)
BehavioralMeal timing is personalized to chronotype (morning/intermediate/evening) determined with the Munich Chronotype Questionnaire (MCTQ). Plans target an earlier first meal and completion of the last meal ≥3-4 h before habitual bedtime, with an eating window of \~10 h/day on ≥6 days/week, adjusted to chronotype using stepwise phase-advance strategies where needed. Diet composition follows bariatric guidelines (protein, hydration, micronutrients). Timing logs and wearables track adherence; visits at 3, 6, and 12 months.
Change in weight maintenance and insulin sensitivity
Evaluate the effect of personalized chrono-nutrition interventions (early time-restricted eating and chronotype-based nutrition) on weight loss maintenance and insulin sensitivity in post-bariatric patients.
Change in gut microbiota diversity and composition
Assess alpha/beta diversity, SCFA production, and bile acid profiles
Change in circadian gene expression and epigenetic markers
DNA methylation (CLOCK, BMAL1, PER2, CRY1), histone modifications (H3Kac, H3K4me3, H3K27me3), and qRT-PCR expression (BMAL1, CLOCK, PPARα, GLUT4
Change in gut-derived hormones
Fasting ghrelin, GLP-1, and PYY
Change in inflammatory markers and lipid profile
CRP, IL-6, TNF-α, total cholesterol, HDL, LDL, triglycerides
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King Saud University
Lead sponsor
King Saud Medical City
Collaborator
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