Obesity & OverweightNCT07672821
Time-Restricted Eating After Bariatric Surgery
A study testing Time-Restricted Eating (16:8) in people with Obesity & Overweight and Bariatric Surgery, run by Medipol University at 2 sites in Turkey (Türkiye).
Trial summary
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… Read more about this study
- Who is it for?
- Ages 18 to 65 years
- Conditions the study is for
- Obesity & Overweight, Bariatric Surgery, Weight Regain
- What is being tested?
- Time-Restricted Eating (16:8)
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 2 sitesTurkey (Türkiye)
- Study dates
- 12 Jul 2025to 12 Jul 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
2 sites in 1 country. Contact the study team or a site near you to ask about taking part.
Turkey (Türkiye)2 sites, 2 recruiting
- Recruiting
Nev Sağlık Grubu
Bursa, Lütfen Seçiniz., 16940
gulsen.ozduran@mudanya.edu.tr
- Recruiting
Nev Sağlık Grubu
Bursa, 16940
Nev Sağlık Grubu dallı Seher ŞEN, Assistant Professor, 05393919700, seherdalli@gmail.com
About this study
Official title: Comparison of Time-Restricted Intermittent Fasting Diet in Individuals With and Without Bariatric Surgery
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).
Read the detailed description
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.
- Conditions
- Obesity & Overweight, Bariatric Surgery, Weight Regain, Weight Regain Post Bariatric Surgery, Time Restricted Feeding
- Being tested
- Time-Restricted Eating (16:8)
- Keywords
- Time-Restricted Eating, Intermittent Fasting, Bariatric Surgery, Obesity, Weight Regain, Anthropometric Measurements, Nutritional Assessment
- Medical subject headings
- Obesity, Overweight, Intermittent Fasting
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Time-Restricted Eating (16:8)Behavioural
Also called 16/8 Fasting
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.
| Study group | Role | What they receive |
|---|---|---|
| Arm 1: Adults with Obesity (Non-Bariatric) | Active comparator | Adults with obesity who have not undergone bariatric surgery. Will follow 16:8 TRE protocol for 6 weeks. Receives: Behavioral: Time-Restricted Eating (16:8) |
| Arm 2: Adults with Obesity (Post-Bariatric) | Experimental | Adults with obesity who experienced insufficient weight loss or weight regain following bariatric surgery. Will follow 16:8 TRE protocol for 6 weeks. Receives: Behavioral: Time-Restricted Eating (16:8) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Body Weight
Change in body weight measured by digital scale
Measured: Baseline and 6 weeks
Body Mass Index (BMI)
Change in BMI calculated as weight (kg) divided by height squared (m²)
Measured: Baseline and 6 weeks
Body Fat Mass
Change in fat mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Measured: Baseline and 6 weeks
Muscle Mass
Change in muscle mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Measured: Baseline and 6 weeks
Waist Circumference
Change in waist circumference measured at 5 cm below the navel
Measured: Baseline and 6 weeks
Hip Circumference
Change in hip circumference measured at the maximum point of gluteal muscles
Measured: 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
Measured: 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.
Measured: Baseline and 6 weeks
Secondary outcomes (2)
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.
Measured: 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.
Measured: Baseline and 6 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Jun 2026
- Study start12 Jul 2025
- Primary completionJun 2026 (estimated)
- Study completion12 Jul 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Obesity & OverweightStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Medipol University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Seher Şen, Mudanya University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07672821
- Sponsor's protocol ID
- MUDU-SBE-SS-04
- Status last verified
- Jun 2026
- First submitted
- 23 Jun 2026
- Last updated
- 29 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Individual participant data will not be shared due to participant confidentiality and institutional data privacy regulations.
Study at a glance
From the registry record, last updated by the sponsor on 29 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Comparison of Time-Restricted Intermittent Fasting Diet in Individuals With and Without Bariatric Surgery
- ClinicalTrials.gov ID
- NCT07672821
- Acronym / sponsor ID
- MUDU-SBE-SS-04
- Conditions
- Obesity & Overweight, Bariatric Surgery, Weight Regain, Weight Regain Post Bariatric Surgery, Time Restricted Feeding
- Keywords
- Time-Restricted Eating, Intermittent Fasting, Bariatric Surgery, Obesity, Weight Regain, Anthropometric Measurements, Nutritional Assessment
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Medipol UniversityUniversity, hospital or other
- Study start
- 12 Jul 2025 (actual)
- Primary completion
- Jun 2026 (estimated)
- Study completion
- 12 Jul 2026 (estimated)
- First posted
- 29 Jun 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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).
Detailed description
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Arm 1: Adults with Obesity (Non-Bariatric) | Active comparator | Behavioral: Time-Restricted Eating (16:8)Adults with obesity who have not undergone bariatric surgery. Will follow 16:8 TRE protocol for 6 weeks. |
| Arm 2: Adults with Obesity (Post-Bariatric) | Experimental | 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. |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- 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
Key exclusion criteria (3 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Time-Restricted Eating (16:8)Also: 16/8 FastingParticipants 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. | Behavioural | Arm 1: Adults with Obesity (Non-Bariatric), Arm 2: Adults with Obesity (Post-Bariatric) |
Primary outcome
Body Weight
Time frame: Baseline and 6 weeks
Change in body weight measured by digital scale
Body Mass Index (BMI)
Time frame: Baseline and 6 weeks
Change in BMI calculated as weight (kg) divided by height squared (m²)
Body Fat Mass
Time frame: Baseline and 6 weeks
Change in fat mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Muscle Mass
Time frame: Baseline and 6 weeks
Change in muscle mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA)
Waist Circumference
Time frame: Baseline and 6 weeks
Change in waist circumference measured at 5 cm below the navel
Hip Circumference
Time frame: Baseline and 6 weeks
Change in hip circumference measured at the maximum point of gluteal muscles
Percentage of Excess Weight Loss (%EWL)
Time frame: Baseline and 6 weeks
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
Percentage of Total Weight Loss (%TWL)
Time frame: Baseline and 6 weeks
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.
2 secondary outcomes
Daily Energy Intake
Time frame: Baseline and 6 weeks
Dietary Macronutrient Distribution
Time frame: Baseline and 6 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Jun 2026.
- Individual participant dataSharing planned: No. Individual participant data will not be shared due to participant confidentiality and institutional data privacy regulations.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Time-Restricted Eating (16:8) in people with Obesity & Overweight and Bariatric Surgery, run by Medipol University at 2 sites in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 29 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Seher Şen, Assistant Professor (+905393919700, seherdalli@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Body Weight (time frame: Baseline and 6 weeks). The study lists 8 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Jun 2026.