Bariatric Surgery, Obesity & Overweight, Time Restricted Feeding, Weight Regain, Weight Regain Post Bariatric Surgery
Conditions
Keywords
Time-Restricted Eating, Intermittent Fasting, Bariatric Surgery, Obesity, Weight Regain, Anthropometric Measurements, Nutritional Assessment
Brief 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 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.
Interventions
BEHAVIORALTime-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.
Sponsors
Medipol University
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
* 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
Exclusion criteria
* 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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Body Weight | Baseline and 6 weeks | Change in body weight measured by digital scale |
| Percentage of Total Weight Loss (%TWL) | 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. |
| Hip Circumference | Baseline and 6 weeks | Change in hip circumference measured at the maximum point of gluteal muscles |
| Percentage of Excess Weight Loss (%EWL) | 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 |
| Body Mass Index (BMI) | Baseline and 6 weeks | Change in BMI calculated as weight (kg) divided by height squared (m²) |
| Body Fat Mass | Baseline and 6 weeks | Change in fat mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA) |
| Muscle Mass | Baseline and 6 weeks | Change in muscle mass assessed by bioelectrical impedance analysis (Tanita MC-780 MA) |
| Waist Circumference | Baseline and 6 weeks | Change in waist circumference measured at 5 cm below the navel |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Daily Energy Intake | Baseline and 6 weeks | 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 | Baseline and 6 weeks | 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. |
Countries
Turkey (Türkiye)
Contacts
CONTACTSeher Şen, Assistant Professor
Outcome results
None listed