NCT Number: NCT06963437
Study Objective:
The aim of this study is to evaluate the effects of revisional bariatric surgery (RBS), very low-calorie ketogenic diet (VLCKD), and intermittent fasting (IF) on nutritional habits and clinical outcomes (anthropometric and biochemical measurements) in patients with insufficient weight loss (IWL) or weight regain (WR) after bariatric surgery, and to compare these findings with those of a control group.
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Notify Me18 year–45 year
All sexes
Interventional
Not applicable
Özel Nev FSM Hastanesi, Bursa, Turkey (Türkiye)
Study Hypotheses:
Healthy volunteers accepted: No
Only the study team can determine whether someone qualifies for participation.
Inclusion criteria
IWL is defined as <50% excess weight loss (EWL) 18 months postoperatively. WR is defined as >25% regain of the lost weight (from the lowest achieved weight).
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Exclusion criteria
A four-stage dietary program will be implemented in accordance with ASMBS guidelines. To the best of our knowledge, there is currently no study comparing the dietary approach following revisional bariatric surgery with ketogenic and intermittent fasting diets
Other names: bariatric diet
A high-protein Very Low-Calorie Ketogenic Diet (VLCKD) will be implemented as the nutritional intervention. In line with previous studies, the daily energy intake of the ketogenic diet will be planned as 600-800 kcal, with approximately 10% of energy from carbohydrates (<30 g/day), 40-45% from protein, and 40-50% from fat. Total carbohydrate intake will be restricted to less than 30 g per day, primarily from vegetables, while fat intake will derive from natural protein sources and 10 g of olive oil per day.
Patients in this group will follow a time-restricted eating pattern (16/8) for a duration of 6 weeks, with food intake limited to an 8-hour window each day. Intermittent fasting will preferably be observed between 6:00 PM and 10:00 AM; however, patients may choose alternative 16-hour fasting periods such as 7:00 PM-11:00 AM or 8:00 PM-12:00 PM, depending on their individual routines. During the 8-hour feeding window, patients will adhere to the stage 4 post-bariatric dietary guidelines in accordance with ASMBS recommendations
Other names: intermittent fasting
No individualized diet will be planned
Other names: Control Group
Time frame: Baseline and Week 6
Body weight will be measured at baseline and at Week 6 using a calibrated digital scale while participants are wearing light clothing and no shoes. Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p<0.05 considered significant.
Time frame: Baseline and Week 6
BMI will be calculated as weight (kg) divided by the square of height (m²), using body weight and height measurements obtained with a digital scale and a wall-mounted stadiometer.
Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p<0.05 considered significant.
Time frame: Baseline and Week 6
Waist circumference will be measured using a non-elastic measuring tape while participants are standing upright. The measurement will be taken 5 cm below the umbilicus.
Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p<0.05 considered significant.
Time frame: Baseline and Week 6
Body composition parameters, including fat mass (%), fat-free mass (%), muscle mass (%), and ECW/TBW ratio, will be assessed using multi-frequency segmental bioelectrical impedance analysis (BIA) (Tanita MC-780 MA, Korea). Assessments will follow ESPEN guidelines.
Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p<0.05 considered significant.
Time frame: Baseline and Week 6
%WL will be calculated using the formula: [(Preoperative weight - Postoperative weight) / Preoperative weight] × 100
Time frame: Baseline and Week 6
%EWL will be calculated using the formula: [(Preoperative weight - Postoperative weight) / (Preoperative weight - Ideal weight)] ×100 *Ideal weight is defined as the weight corresponding to a BMI of 25 kg/m².*
Time frame: Baseline and Week 6
Fasting venous blood samples will be collected after an overnight fast of at least 8 hours, both at baseline and at Week 6. Fasting blood glucose will be measured using standardized automated analyzers in a certified clinical laboratory.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Serum insulin concentrations will be determined from fasting blood samples taken at baseline and Week 6 using standardized laboratory methods.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Lipid levels will be assessed from fasting blood samples. The lipid profile includes high- density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol, and triglycerides.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Renal function parameters will be analyzed using fasting blood samples to determine changes in blood urea nitrogen (BUN), creatinine, uric acid, and urea levels.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Liver function will be assessed by measuring serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, and total protein.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Serum concentrations of vitamins and minerals will be measured from fasting samples. Parameters include vitamin B12, folic acid, magnesium, total calcium, sodium, and potassium.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Hematological status will be evaluated using fasting blood samples to assess hemoglobin, hematocrit, ferritin, serum iron, and total iron binding capacity (TIBC).Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Daily intake of energy (kcal/day) and macronutrients-protein, fat, carbohydrate, and fiber (g/day)-will be assessed using 3-day dietary records (including one weekend day) and a validated Food Frequency Questionnaire (FFQ). Data will be analyzed using BEBIS-9 (Nutrition Information System, Turkey). Dietary records will be reviewed for completeness and accuracy by trained dietitians. Results will be reported in kcal/day and g/day.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Time frame: Baseline and Week 6
Micronutrient intake (e.g., vitamins and minerals) will be assessed using 3-day dietary records and the FFQ. Data will be analyzed using BEBIS-9, with results reported in standard units (e.g., mg/day, µg/day). Intake values will be interpreted in relation to dietary reference values but without applying a composite scoring scale.
Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.
Medipol University
Other
Comparison of Revisional Surgery, Ketogenic Diet, and Intermittent Fasting in Bariatric Surgery Patients With Weight Regain: A Prospective Randomized Controlled Study
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View the official ClinicalTrials.gov record (opens in a new tab)This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.
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