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What change in body mass index is associated with improvement in percentage body fat in childhood obesity? A meta-regression
  1. Laura Birch1,
  2. Rachel Perry1,
  3. Linda P Hunt1,
  4. Rhys Matson1,
  5. Amanda Chong1,
  6. Rhona Beynon1,
  7. Julian PH Shield1,2
  1. 1 NIHR Bristol Biomedical Research Centre—Nutrition theme, Level 3 University Hospitals Bristol Education Centre, Bristol, UK
  2. 2 University Hospitals Bristol NHS Foundation Trust, Level 6 University Hospitals Bristol Education Centre, Bristol, UK
  1. Correspondence to Laura Birch; laura.birch{at}


Objective Using meta-regression this paper sets out the minimum change in body mass index-SD score (BMI-SDS) required to improve adiposity as percentage body fat for children and adolescents with obesity.

Design Meta-regression.

Setting Studies were identified as part of a large-scale systematic review of the following electronic databases: AMED, Embase, MEDLINE via OVID, Web of Science and CENTRAL via Cochrane library.

Participants Individuals aged 4–19 years with a diagnosis of obesity according to defined BMI thresholds.

Interventions Studies of lifestyle treatment interventions that included dietary, physical activity and/or behavioural components with the objective of reducing obesity were included. Interventions of <2 weeks duration and those that involved surgical and/or pharmacological components (eg, bariatric surgery, drug therapy) were excluded.

Primary and secondary outcome measures To be included in the review, studies had to report baseline and post-intervention BMI-SDS or change measurements (primary outcome measures) plus one or more of the following markers of metabolic health (secondary outcome measures): adiposity measures other than BMI; blood pressure; glucose; inflammation; insulin sensitivity/resistance; lipid profile; liver function. This paper focuses on adiposity measures only. Further papers in this series will report on other outcome measures.

Results This paper explores the potential impact of BMI-SDS reduction in terms of change in percentage body fat. Thirty-nine studies reporting change in mean percentage body fat were analysed. Meta-regression demonstrated that reduction of at least 0.6 in mean BMI-SDS ensured a mean reduction of percentage body fat mass, in the sense that the associated 95% prediction interval for change in mean percentage body fat was wholly negative.

Conclusions Interventions demonstrating reductions of 0.6 BMI-SDS might be termed successful in reducing adiposity, a key purpose of weight management interventions.

Trial registration number CRD42016025317.

  • obesity
  • childhood
  • adolescence
  • body mass index
  • body fat

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  • Contributors LB and RP provided substantial contributions to the conception and design of the study, designed the data extraction instrument, performed electronic database searches, data screening, extraction and quality assessment, coordinated and supervised data collection and drafted and revised the manuscript. JPHS provided a substantial contribution to the conception and design of the study, conducted data screening and interpretation and assisted with drafting and revision of the manuscript. LPH provided statistical expertise in relation to study design and conducted the data analyses and contributed to the drafting and revision of the manuscript. RM, AC and RB were involved in data acquisition and management. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

  • Funding This study was supported by the NIHR Biomedical Research Centre at the University Hospitals Bristol NHS Foundation Trust and the University of Bristol.

  • Competing interests JPHS and LPH are authors on two studies included in the systematic review that this paper reports on.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Dataset will be available from the Dryad repository (not yet set up so DOI currently unavailable).

  • Patient consent for publication Not required.

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