Identifying the best body mass index metric to assess adiposity change in children.

ABSTRACT: OBJECTIVE:Although dual-energy X-ray absorptiometry (DEXA) is the preferred method to estimate adiposity, body mass index (BMI) is often used as a proxy. However, the ability of BMI to measure adiposity change among youth is poorly evidenced. This study explored which metrics of BMI change have the highest correlations with different metrics of DEXA change. METHODS:Data were from the Quebec Adipose and Lifestyle Investigation in Youth cohort, a prospective cohort of children (8-10?years at recruitment) from Québec, Canada (n=557). Height and weight were measured by trained nurses at baseline (2008) and follow-up (2010). Metrics of BMI change were raw (?BMIkg/m(2) ), adjusted for median BMI (?BMIpercentage) and age-sex-adjusted with the Centers for Disease Control and Prevention growth curves expressed as centiles (?BMIcentile) or z-scores (?BMIz-score). Metrics of DEXA change were raw (total fat mass; ?FMkg), per cent (?FMpercentage), height-adjusted (fat mass index; ?FMI) and age-sex-adjusted z-scores (?FMz-score). Spearman's rank correlations were derived. RESULTS:Correlations ranged from modest (0.60) to strong (0.86). ?FMkg correlated most highly with ?BMIkg/m(2) (r?=?0.86), ?FMI with ?BMIkg/m(2) and ?BMIpercentage (r?=?0.83-0.84), ?FMz-score with ?BMIz-score (r?=?0.78), and ?FMpercentage with ?BMIpercentage (r?=?0.68). Correlations with ?BMIcentile were consistently among the lowest. CONCLUSIONS:In 8-10-year-old children, absolute or per cent change in BMI is a good proxy for change in fat mass or FMI, and BMI z-score change is a good proxy for FM z-score change. However change in BMI centile and change in per cent fat mass perform less well and are not recommended.

SUBMITTER: Kakinami L 

PROVIDER: S-EPMC4215345 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature