Validity of non‐traditional measures of obesity compared to total body fat across the life course: A systematic review and meta‐analysis

IntroductionTraditional obesity measures including body mass index, waist circumference, waist-to-hip ratio, and waist-to-height ratio have limitations. The primary objective of this study was to identify and review the validity of non-traditional obesity measures, using measures of total body fat as the reference standard, that have been used across multiple life stages. MethodsWe conducted a systematic review and searched MEDLINE, Embase, and PsycINFO. We included observational studies published from 2013 to October 2023 among "the general population" for any life stage that reported the validity of non-traditional obesity measures compared to total body fat reference standards. Separate meta-analyses were performed to pool correlation coefficients and mean differences for non-traditional obesity measures that were evaluated at multiple life stages. ResultsA total of 123 studies were included, and 55 validated non-traditional obesity measures were identified. Of these, 13 were evaluated at multiple life stages. Two-dimensional (2D) digital imaging technologies, three-dimensional (3D) body scanners, relative fat mass (RFM), and mid-upper arm circumference had high or moderate validity (pooled correlation coefficient >0.70). Pooled mean differences were small (<6%) between total body fat percentage from reference standards and from RFM, 2D digital imaging technologies, 3D body scanners, and the body adiposity index. Heterogeneity (I²) was >75% in most meta-analyses. ConclusionNumerous validated non-traditional obesity measures were identified; relatively few were evaluated at multiple life stages and did not consider health risks associated with adiposity. More research is needed to define valid obesity measures across all life stages that assess health and adiposity.