A COM-B-guided lifestyle intervention reduces metabolic syndrome in overweight and obese adolescents: a multiphase study in Vietnam.

Metabolic syndrome (MetS) among adolescents with overweight/obesity (OW/OB) is rising rapidly in low- and middle-income countries (LMICs), yet evidence on theory-driven behavioral interventions remains limited. To estimate the prevalence and risk factors of MetS in Vietnamese adolescents aged 11-14 years with OW/OB, and to evaluate the effectiveness of a 12-month lifestyle intervention grounded in the COM-B model. We conducted a three-phase study: (1) a province-wide cross-sectional survey to determine MetS prevalence; (2) a matched case-control study to identify risk factors; and (3) a school-based COM-B intervention comprising health education, environmental modifications, and motivation enhancement. Adherence was quantified using a six-point scale and categorized as high (≥ 75%), moderate (40-<75%), or low (< 40%). The primary outcome was MetS resolution at 12 months according to International Diabetes Federation (IDF) pediatric criteria; secondary outcomes included anthropometric, biochemical, and behavioral changes. Of 6,009 students screened, 2,055 (34.2%) had OW/OB, among whom 628 (30.6%; 95% CI, 28.6-32.6) had MetS, with hypertriglyceridemia (87.9%) and low HDL-C (84.4%) being most prevalent. Waist-to-height ratio ≥ 0.46 was the strongest independent risk factor (OR = 2.96; 95% CI: 1.76-5.00), while exclusive breastfeeding for 6 months was protective (OR = 0.45; 95% CI: 0.35-0.58). A 12-month COM-B-guided lifestyle intervention in 300 OW/OB adolescents with MetS achieved a 71.7% resolution rate (95% CI: 66.2-76.7), with significant improvements in metabolic parameters (triglycerides - 0.41 mmol/L, HDL-C + 0.12 mmol/L, CAP - 29.6 dB/m; all p < 0.001) and health behaviors (sugar-sweetened beverage intake - 4.7 times/week, screen time - 3.6 h/day). High adherence was associated with the greatest cardiometabolic and behavioral gains, supporting a dose-response relationship consistent with the COM-B framework. A school-based COM-B intervention substantially improved MetS and health behaviors among adolescents with OW/OB, with effectiveness varying by adherence level. The model appears feasible and scalable in LMIC settings, although longer-term follow-up is needed to assess sustainability.