Longitudinal changes in BMI z-scores among 45 414 2–4-year olds with severe obesity. (17th November 2017)

• Record Type: Journal Article
• Authors: Freedman, David S.; Butte, Nancy F.; Taveras, Elsie M.; Goodman, Alyson B.; Blanck, Heidi M.
• Is Part Of: Annals of human biology. Volume 44:Number 8(2017)
• Page Start: 687
• Page End: 692
• Publication Date: 2017-11-17
• Subjects: BMI -- longitudinal -- children -- LMS; Human biology -- Periodicals; 612
• DOI: 10.1080/03014460.2017.1388845
• Languages: English
• ISSNs: 0301-4460

Abstract

Abstract: Background: BMI z -scores (BMI z ) based on the Centers for Disease Control and Prevention (CDC) growth charts among children do not accurately characterise BMI levels among children with very high BMIs. These limitations may be particularly relevant in longitudinal and intervention studies, as the large changes in the L (normality) and S (dispersion) parameters with age can influence BMI z . Aim: To compare longitudinal changes in BMI z with BMI expressed as a percentage of the 95th percentile (%BMIp95) and a modified z -score calculated as log(BMI/M)/S. Subjects and methods: A total of 45 414 2–4-year-olds with severe obesity (%BMIp95 ≥ 120). Results: Changes in very high BMI z levels differed from the other metrics. Among severely obese 2-year-old girls, for example, the mean BMI z decreased by 0.6 SD between examinations, but there were only small changes in BMIp95 and modified BMI z . Some 2-year-old girls had BMI z decreases of >1 SD, even though they had large increases in BMI, %BMIp95 and modified BMI z . Conclusions: Among children with severe obesity, BMI z changes may be due to differences in the transformations used to estimate levels of BMI z rather than to changes in body size. The BMIs of these children could be expressed relative to the 95th percentile or as modified z -scores.