Introduction There has been a steep increase in the prevalence of adolescent overweight and obesity globally and in India, demonstrating that present prevention strategies are insufficient. Available evidence suggests that multifactorial interventions may improve short-term physical activity (PA), nutrition and psychological behaviour of overweight and obese adolescents but long-term follow-ups and strategies are needed. This study will investigate the effects of a structured multifactorial (school-based and family-based) intervention on adolescent obesity, compared with a single or no intervention. Methods and analysis A pragmatic, clustered randomised controlled trial with 12 weeks of interventions and 3-month, 6-month and 12-month follow-ups will be conducted at multiple participating schools in Karnataka, India. The participants will be overweight and obese male and female adolescents aged 11-16 years and will be randomly assigned by school into three groups: group A (multifactorial intervention, exercise and dietary advice); group B (exercise only); and group C (controls, no interventions). Primary outcome measures are the level of PA and body composition. Secondary outcomes are dietary change, behaviour change, food behaviours, cardiovascular and muscular fitness, quality of life, parental behaviours (physical and mental) and family functioning. Positive intervention results may reduce obesity in adolescents and promote a healthier lifestyle for students and families. A larger, culturally diverse population can benefit from a similar methodology. Ethics and dissemination The study has been approved by the Institutional Research and Ethics Committee (IEC 536-2018), Kasturba Hospital, Manipal, Udupi District, Karnataka, India. A written and verbal informed consent (supplemental material) will be provided to the participants prior to participation. On completion of the trial, the results can be communicated to adolescents and their parents on request, and will be published at national and international conferences and in peer-reviewed journals. Trial registration number CTRI/2019/04/018834.
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