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).
Patients with a BMI ≥ 35 kg/m², regardless of the presence of comorbidities
Patients with a BMI of 30-34.9 kg/m² who have an obesity-related metabolic disease and are considered eligible for surgical treatment
Patients who have undergone metabolic and bariatric surgery (MBS) in accordance with current ASMBS/IFSO guidelines (Eisenberg et al., 2022)
Patients under regular postoperative follow-up
Inflammatory bowel disease
History of upper gastrointestinal bleeding
Severe psychiatric disorders
Active cancer diagnosis
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.
Cohort
Prospective
Collagen-containing supplement
Dietary supplementCollagen-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.
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.
Change in Body Mass Index (BMI)
BMI calculated as body weight (kg) divided by height squared (m²).
Percentage of Total Weight Loss (%TWL)
Calculated as (preoperative weight - postoperative weight) / preoperative weight × 100.
Change in Fasting Blood Glucose
Fasting blood glucose (mg/dL) obtained from routine clinical laboratory follow-up.
Change in Fasting Insulin
Fasting insulin (µIU/mL) obtained from routine clinical laboratory follow-up.
Change in HbA1c
Glycated hemoglobin (HbA1c, %) obtained from routine clinical laboratory follow-up.
Change in LDL Cholesterol
LDL cholesterol (mg/dL) obtained from routine clinical laboratory follow-up.
Click on the lead sponsor to view all of their trials.
