School and Family-Based Obesity Prevention in Pakistani Primary School Children

Study Design: Two-phase, prospective, parallel-group, cluster-randomized controlled trial (cRCT) with an embedded mixed-methods process evaluation and longitudinal sustainability follow-up. Phase 1: 9-month primary efficacy trial. Phase 2: sustainability assessment at 12 months from baseline (3 months post-intervention).

Setting: 26 primary schools from three cities in Punjab, Pakistan: Lahore, Sahiwal, and Bahawalnagar. These cities represent the socioeconomic and cultural diversity of Punjab, the most populous province of Pakistan.

Randomization: Schools will be randomized 1:1 to intervention or control using computer-generated sequence, stratified by study site. An independent statistician will perform allocation concealment. Outcome assessors and the statistician will be blinded to group assignment. Participants, parents, and school personnel cannot be blinded due to the behavioral nature of the intervention.

Sample Size: 26 schools (13 intervention, 13 control), approximately 90 children per school, total 2,340 children aged 6-12 years in grades 3-5. Sample size calculation assumed a reduction in overweight/obesity prevalence from 36.7% to 26.7% (10% absolute reduction), 80% power, α=0.05, coefficient of variation k=0.15, and 20% attrition buffer.

Intervention (9 months): Developed using the Social Ecological Model and informed by a systematic review (PROSPERO CRD420251242889). Components include:

Child-focused: 18 biweekly sessions (40 min each) of health education (nutrition, physical activity, screen time reduction) and thematic workshops; daily 45 minutes of moderate-to-vigorous physical activity; monthly BMI measurement by trained staff; weekly self-weighing.

Parent-focused: Three workshops covering health messages, WhatsApp training, and feedback on child's progress; encouragement of 30-60 minutes of daily physical activity outside school.

mHealth component: Weekly automated WhatsApp/SMS messages with health tips and behavior tracking; monthly personalized feedback on child's BMI and behavior change. Tiered system for parents without smartphones (SMS or paper booklets).

Fidelity monitoring: Regular field observations, digital engagement logs, and process evaluation.

Control: Schools continue usual curriculum without any structured obesity prevention program. Routine physical education classes, standard school health checks if available, and no structured nutrition education or family engagement activities. After the 12-month follow-up, control schools receive intervention materials.

Outcomes:

Primary: Change in prevalence of overweight and obesity (WHO BMI-for-age z-score: overweight >+1 SD, obesity >+2 SD) from baseline to 9 months.

Secondary: Change in BMI z-score, waist circumference, body fat percentage, moderate-to-vigorous physical activity (days/week ≥60 min), daily screen time, dietary behaviors (sugar-sweetened beverages, fried foods, fast food), obesity-related knowledge (child), parental knowledge and self-efficacy, physical fitness (rope jumps, sit-ups, standing jump, shuttle run), and sustainability of BMI z-score change at 12 months.

Data Collection: Baseline (month 0), mid-point (month 6), post-intervention (month 9), sustainability follow-up (month 12). Anthropometric measurements (height, weight, waist/hip circumference, body fat percentage), blood pressure, physical fitness tests, and validated child/parent questionnaires.

Statistical Analysis: Intention-to-treat principle using generalized linear mixed models accounting for clustering. Primary outcome: binary prevalence analyzed with binomial distribution and logit link, adjusting for baseline values and stratification factors. Secondary continuous outcomes: mixed models with random intercept for school. Missing data <5% will use maximum likelihood; >5% sensitivity with last-value-carried-forward. Subgroup analyses by region, sex, maternal education, baseline BMI status, and primary caregiver. All tests two-sided α=0.05. Analysis will use SAS 9.4.

Process Evaluation: Concurrent mixed-methods evaluation guided by the EPIS framework to assess fidelity, dose, reach, adaptation, barriers, and facilitators. Quantitative metrics (reach, adoption, implementation fidelity, engagement logs) and qualitative interviews/focus groups with principals, teachers, and parents.

Ethics: Approved by Central South University Institutional Review Board (approval number XYGW-2026-18). Written parental consent and child verbal assent required. Data anonymized and securely stored. Study follows Declaration of Helsinki and local guidelines.

Trial Status: Recruitment began December 8, 2025. Planned primary completion September 8, 2026; study completion December 8, 2026.

Funding/Support: National Natural Science Foundation of China (as per proposal page 1). Sponsor: Central South University.