An interventional study of Time-Restricted Eating (16:8) in Obesity & Overweight, Bariatric Surgery and Weight Regain, sponsored by Medipol University. Recruiting at 2 sites in Turkey (Türkiye). Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-06-29.
Sponsored by Medipol University · Not applicable, Interventional, and Treatment
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).
Obesity remains a major global health concern, with bariatric surgery (BS) being the most effective treatment for severe obesity. However, some patients experience insufficient weight loss (IWL) or weight regain (WR) approximately 18 months after surgery, which is associated with recurrence of obesity-related comorbidities and reduced quality of life.
Time-restricted eating (TRE), a form of intermittent fasting, has emerged as a promising dietary approach for obesity management. The 16/8 TRE model, which limits food intake to an 8-hour window, has shown beneficial effects on body weight, insulin resistance, glycemic control, and lipid profiles in non-surgical individuals with obesity. However, evidence regarding its efficacy and safety in post-bariatric surgery patients remains limited.
This prospective controlled study will enroll 40 adults with obesity (20 per group): Group 1 - adults with obesity who have not undergone BS; Group 2 - adults with IWL or WR following BS. All participants will follow a 16:8 TRE protocol for 6 weeks, with nutritional principles aligned with ASMBS guidelines. Follow-up visits will be conducted face-to-face at baseline, day 15, day 30, and day 45, with additional weekly contact via phone or WhatsApp. Anthropometric measurements will be assessed at baseline and at week 6. Dietary intake will be evaluated using 3-day food records and food frequency questionnaires, analyzed with the BEBİS-9 nutrition software.
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This study's planned enrollment of 40 is below the median of 67 across 9,006 interventional studies indexed under Obesity.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adults with obesity who have not undergone bariatric surgery. Will follow 16:8 TRE protocol for 6 weeks.
Behavioral: Time-Restricted Eating (16:8)
Adults with obesity who experienced insufficient weight loss or weight regain following bariatric surgery. Will follow 16:8 TRE protocol for 6 weeks.
Behavioral: Time-Restricted Eating (16:8)
Participants 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.
Also known as: 16/8 Fasting
Body Weight
Change in body weight measured by digital scale
Time frame: Baseline and 6 weeks
Body Mass Index (BMI)
Change in BMI calculated as weight (kg) divided by height squared (m²)
Time frame: Baseline and 6 weeks
Body Fat Mass
Change in fat mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Time frame: Baseline and 6 weeks
Muscle Mass
Change in muscle mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Time frame: Baseline and 6 weeks
Waist Circumference
Change in waist circumference measured at 5 cm below the navel
Time frame: Baseline and 6 weeks
Hip Circumference
Change in hip circumference measured at the maximum point of gluteal muscles
Time frame: Baseline and 6 weeks
Percentage of Excess Weight Loss (%EWL)
Calculated as: \[(preoperative weight - postoperative weight) / (preoperative weight - ideal weight)\] × 100. Ideal body weight defined based on a BMI of 25 kg/m². Insufficient weight loss (IWL) defined as
Time frame: Baseline and 6 weeks
Percentage of Total Weight Loss (%TWL)
Calculated as: \[(preoperative weight - postoperative weight) / preoperative weight\] × 100. Used to assess overall weight loss outcomes in both bariatric and non-bariatric participants following the 6-week time-restricted eating intervention.
Time frame: Baseline and 6 weeks
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.
Time frame: Baseline and 6 weeks
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.
Time frame: Baseline and 6 weeks
Plan to share: No — Individual participant data will not be shared due to participant confidentiality and institutional data privacy regulations.
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