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).
Study Type
OBSERVATIONAL
Enrollment
52
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
Yıldırım Doruk Hastanesi
Bursa, Yıldırım, Turkey (Türkiye)
RECRUITINGChange 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.
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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