An observational study in Obesity & Overweight, Collagen Protein and Bariatric Surgery, sponsored by Mudanya University. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-09.
Sponsored by Mudanya University · Observational
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Among 353 studies in Obesity with a site in Turkey — 73 open to participants now, 91 under way, 16 of them phase 3. Obesity · Turkey.
Among the 353 studies in Obesity with a site in Turkey, this one is the 116th largest by planned enrollment of the 160 observational ones that give a count, is one of 60 that started in 2026, is one of 160 observational ones, reaches primary completion later than 52 of the 90 other live ones, and was the 313th registered.
11,529 studies on the registry are indexed under Obesity; 2,035 are open to participants now.
Browse Obesity studies →73 of the 353 studies in Obesity with a site in Turkey are open now. Recruiting first, the newest first:
Pamukkale University · Sites in Turkey
Ages 18–65 · Women only
Gazi University · Sites in Turkey
Ages 50–60 · Women only
Duzce University · Sites in Turkey
Ages 18+
Pamukkale University · Sites in Turkey
Ages 18–60 · Women only
Kocaeli University · Sites in Turkey
Ages 18–65 · Healthy volunteers
A study can be open while its sites in Turkey have not opened yet or have stopped. Only those recruiting at a site in Turkey →
Of the 1,336 Obesity studies recruiting now, 377 (28%) set no upper age limit and 856 (64%) stop at 75 or younger; 166 take children under 18; 488 take healthy volunteers.
This study: 18 Years to 65 Years · all sexes · healthy volunteers too.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
353 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 2 3 · Phase 3 27 · Phase 4 3
First in 2005; this study’s year is marked. 60 started in 2026.
By drug class, each counting the studies that test any of its medicines:
This study's planned enrollment of 52 is below the median of 115 across 2,157 observational studies indexed under Obesity.
Median enrollment 64 across the 192 interventional studies, 82 across the 160 observational. Of the 236 that completed or were terminated, 7 (3%) have results posted.
This tab as a report to print or save as PDF → With an account.
34 of 353 have an industry lead sponsor. The 10 most frequent:
Mudanya University is the lead sponsor of 3 studies on the registry; 3 are open to participants now.
Mudanya University has 2 studies filed under Obesity — fewer than ten, so there is no comparison to draw.
35 of the studies in Obesity with a site in Turkey that are under way reach primary completion within a year, 1 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT05556512Phase 3Eli Lilly and CompanyA Study of Tirzepatide (LY3298176) on the Reduction on Morbidity and Mortality in Adults With Obesity | 2027-10 |
| NCT07769736Istinye UniversityMotivational Interviews Based on the Five-Step (5A) Model on Obesity Risk | 2026-11 |
| NCT07652151Fundación Pública Andaluza para la gestión de la Investigación en SevillaUNMASK: Unveiling the Pathobiology of Metabolic Dysfunction-Associated Steatotic Liver Disease for the Discovery of Novel Therapeutics and Biomarkers | 2026-11 |
| NCT07936877Mudanya UniversityIntragastric Balloon and Time-Restricted Eating for Weight Loss in Adults With Overweight or Obesity | 2026-11-15 |
| NCT07878299Sultan Abdulhamid Han Training and Research Hospital, Istanbul, TurkeyComparison of Segmental Body Composition Characteristics in Lipedema and Obesity | 2026-11-20 |
Add all 35 to your calendar (.ics) → With an account.
Among the 353 studies in Obesity with a site in Turkey, from their registry updates:
This tab as a report to print or save as PDF → With an account.
This prospective, observational cohort study aims to evaluate whether the use of collagen-containing supplements is associated with differences in muscle mass, body composition, and body image among patients who have undergone sleeve gastrectomy (SG). The study will be conducted at the General Surgery outpatient clinic of a private hospital in Bursa, Türkiye, between May 2026 and March 2027, and will enroll adult patients (aged 18-65 years) who meet current ASMBS/IFSO eligibility criteria for metabolic and bariatric surgery.
Participants will be naturally allocated into two observational groups based on their own choice to use or not use collagen-containing supplements; no supplement will be provided or recommended by the study team, and no intervention will be made to participants' standard clinical care. All patients will be followed according to routine clinical practice preoperatively and at 2 weeks, 1 month, 3 months, and 6 months postoperatively.
Primary outcome measures include anthropometric parameters (body weight, BMI, fat mass, fat mass percentage, fat-free mass, muscle mass, percentage of weight loss, percentage of excess weight loss, waist and hip circumference) assessed via bioelectrical impedance analysis (Tanita MC-780 MA), and body image assessed using the Turkish-validated Body Shape Questionnaire (BSQ). Secondary outcomes include biochemical parameters, comorbidities, and macronutrient intake data obtained from 3-day dietary records analyzed using the BEBİS nutrition software.
The study hypothesizes that patients using collagen-containing supplements will show significant differences in muscle mass and body composition parameters compared with non-users, and that supplement use will be significantly associated with BSQ scores. A sample size of approximately 52 participants per group was calculated using G*Power 3.1 (one-way ANOVA, Cohen's f = 0.25, α = 0.05, power = 0.80).
Adult patients aged 18-65 years who underwent sleeve gastrectomy and are under routine postoperative follow-up at the General Surgery outpatient clinic of a private hospital in Bursa, Türkiye. Eligible patients meet current ASMBS/IFSO criteria for metabolic and bariatric surgery (BMI ≥ 35 kg/m², or BMI 30-34.9 kg/m² with an obesity-related metabolic comorbidity). Participants are naturally grouped according to their own preference to use or not use a collagen-containing supplement following surgery.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
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.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Group/Cohort Label: Collagen Supplement Users (Kolajen Kullananlar) Description: Participants who, based on their own preference, use a collagen-containing supplement product following sleeve gastrectomy, without any intervention or recommendation from the study team.
Dietary Supplement: Collagen-containing supplement
Group/Cohort Label: Non-Users of Collagen Supplement (Kolajen Kullanmayanlar) Description: Participants who do not use any collagen-containing supplement product following sleeve gastrectomy, followed under routine clinical care.
Collagen-containing supplement products used at the participants' own discretion following sleeve gastrectomy. The type of product, daily dosage, and duration of use were self-reported by participants
Change in Body Weight
Body weight (kg) measured using a Tanita MC-780 MA device.
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Change in Body Shape Questionnaire (BSQ) Score
Body image concerns were assessed using the Body Shape Questionnaire (BSQ-34), a validated instrument for the Turkish population. This 34-item self-report scale evaluates weight-related concerns and dissatisfaction with body shape over the preceding four weeks. Each item is scored from 1 (never) to 6 (always), with a total score range of 34 to 204. Higher scores indicate greater dissatisfaction with body shape, i.e., a worse outcome.
Time frame: Preoperative and postoperative 6 months
Change in Body Mass Index (BMI)
BMI calculated as body weight (kg) divided by height squared (m²).
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Percentage of Total Weight Loss (%TWL)
Calculated as (preoperative weight - postoperative weight) / preoperative weight × 100.
Time frame: Postoperative and 6 months
Percentage of Excess Weight Loss (%EWL)
Calculated as (preoperative weight - postoperative weight) / (preoperative weight - ideal weight) × 100. Ideal body weight was calculated assuming a BMI of 25 kg/m².
Time frame: Postoperative and 6 months
Change in Fat Mass
Fat mass (kg) assessed by multi-frequency bioelectrical impedance analysis (BIA) using a Tanita MC-780 MA device.
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Change in Fat Mass Percentage
Fat mass expressed as a percentage of total body weight, assessed by bioelectrical impedance analysis (BIA) using a Tanita MC-780 MA device.
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Change in Muscle Mass
Muscle mass (kg) assessed by bioelectrical impedance analysis (BIA) using a Tanita MC-780 MA device.
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Change in Muscle Mass Percentage
Muscle mass expressed as a percentage of total body weight, assessed by bioelectrical impedance analysis (BIA) using a Tanita MC-780 MA device.
Time frame: Preoperative, and postoperative 2 weeks, 1 month, 3 months, and 6 months
Change in Fasting Blood Glucose
Fasting blood glucose (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Fasting Insulin
Fasting insulin (µIU/mL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in HbA1c
Glycated hemoglobin (HbA1c, %) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in LDL Cholesterol
LDL cholesterol (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in HDL Cholesterol
HDL cholesterol (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Triglycerides
Triglycerides (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and postoperative 6 months
Change in Total Cholesterol
Total cholesterol (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and postoperative 6 months
Change in ALT
Alanine aminotransferase (ALT, U/L) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in AST
Aspartate aminotransferase (AST, U/L) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Uric Acid
Uric acid (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Urea
Urea (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Hemoglobin
Hemoglobin (g/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Hematocrit
Hematocrit (%) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Ferritin
Ferritin (ng/mL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Serum Iron
Serum iron (µg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Vitamin B12
Vitamin B12 (pg/mL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Folic Acid
Folic acid (ng/mL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Magnesium
Magnesium (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Total Calcium
Total calcium (mg/dL) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Serum Sodium
Serum sodium (mEq/L) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Change in Serum Potassium
Serum potassium (mEq/L) obtained from routine clinical laboratory follow-up.
Time frame: Preoperative and 6 months
Plan to share: No — Individual participant data will not be shared, as this was not planned or consented to as part of the study protocol. Data confidentiality was assured to participants at the time of enrollment, and no data sharing infrastructure or agreement is in place beyond the study team.
No publications or documents are linked to this record.
Started Jul 2026 (actual). Primary completion is estimated for Jan 2027, 6 months after the start.
Of 792 non-industry observational studies under Obesity, half reached primary completion within 40 months of starting (the median), counting those still running; a quarter within 17 and three quarters within 106. This study's planned 6 months is below that.
Counting every sponsor, half of 837 studies reached it within 39 months; a quarter within 17 and three quarters within 96.
How these figures are worked out, and which studies are left out of them.
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Mudanya University