This study aims to compare the effects of time-restricted eating (TRE, 16/8) in adults with obesity who have and have not undergone bariatric surgery (BS). The study will include adults aged 18-65 years: those with obesity who have not undergone BS, and those who have experienced insufficient weight loss (IWL) or weight regain (WR) following BS. Both groups will follow a 16:8 time-restricted eating protocol for 6 weeks, with an 8-hour eating window recommended between 10:00 AM and 6:00 PM, though participants may adjust to other 16-hour fasting windows. Participants will be evaluated before and after the intervention in terms of anthropometric measurements, biochemical parameters, and dietary habits. The study is being conducted at a private hospital in Bursa, Turkey, and is planned to be completed with a total of 40 participants (20 per group).
Adults aged 18-65 years with obesity who have not undergone bariatric surgery
Adults aged 18-65 years with obesity who have undergone bariatric surgery and experienced insufficient weight loss (IWL) within 18 months post-surgery, -defined as %EWL <50% at 18 months
Adults aged 18-65 years with obesity who have undergone bariatric surgery and experienced weight regain (WR), defined as >25% increase in %EWL from the lowest recorded weight
Pregnant or breastfeeding individuals
Acute illness, active infection, or comorbid conditions limiting treatment efficacy and safety, including: cancer, type 1 diabetes, renal or hepatic failure, recent stroke or myocardial infarction, nephrolithiasis, drug or alcohol abuse, eating disorders, severe depression or other psychiatric disorders, inflammatory bowel disease (IBD), neoplasia, arrhythmic heart disease, heart failure, respiratory failure, or corticosteroid therapy
Professional athletes
Parallel
Time-Restricted Eating (16:8)
BehavioralParticipants will follow a 16:8 time-restricted eating protocol for 6 weeks, limiting food intake to an 8-hour window (recommended 10:00 AM-6:00 PM, with flexibility to adjust). During the 16-hour fasting period, only water and non-caloric beverages (tea, coffee, soda) are permitted. Nutritional principles will be aligned with ASMBS guidelines.
Body Weight
Change in body weight measured by digital scale
Body Mass Index (BMI)
Change in BMI calculated as weight (kg) divided by height squared (m²)
Body Fat Mass
Change in fat mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Muscle Mass
Change in muscle mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Daily Energy Intake
Change in daily energy intake (kcal/day) assessed by 3-day dietary records (including one weekend day) and food frequency questionnaire, analyzed using the Nutritional Information System software (BEBİS-9). Data collected through face-to-face interviews at baseline and week 6.
Dietary Macronutrient Distribution
Change in daily macronutrient intake including carbohydrate (%), protein (%), and fat (%) assessed by 3-day dietary records and food frequency questionnaire, analyzed using BEBİS-9 software. Target distribution for post-bariatric participants: carbohydrate 48-55%, protein 23-27%, fat 21-27% of total daily energy intake, in accordance with ASMBS guidelines.
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Medipol University
Lead sponsor
Mudanya University
Sponsor institution
