Abstract Background Childhood obesity is one of the most serious, global, public health challenges and has adverse health consequences in both the short-and long-term. The purpose of this study is to establish the change in body mass index (BMI) needed to achieve improvements in metabolic health status in obese children and adolescents attending lifestyle treatment interventions. Methods The following electronic databases will be searched from their inception: AMED, Embase, MEDLINE via OVID, Web of Science and CENTRAL via Cochrane library. Randomised controlled trials (RCTs) or cohort studies of lifestyle interventions (i.e. dietary, physical activity and/or behavioural therapy) for treating obesity in children and adolescents (4â 18 years) will be included. Interventions that last less than 2 weeks and trials that include overweight participants or those with a secondary or syndromic cause of obesity will not be included. No language restrictions will be applied. Titles and abstracts will be assessed for eligibility by two reviewers, and data from full-text articles will be extracted using a standardised data extraction template. Reference lists of all included articles will be hand-searched for additional publications. A narrative synthesis of the findings will be presented, and meta-analysis will be conducted if considered appropriate. Discussion This will be the first systematic review of studies to establish the change in BMI required to improve metabolic health status in obese children and adolescents. Systematic review registration PROSPERO CRD42016025317