Telford Richard D, Telford Rohan M, Welvaert Marijke
Research Institute for Sport and Exercise, University of Canberra, Australia.
Research Institute for Sport and Exercise, University of Canberra, Australia.
J Sci Med Sport. 2019 Mar;22(3):307-310. doi: 10.1016/j.jsams.2018.08.002. Epub 2018 Aug 8.
Despite evidence suggesting caution, employment of body mass index (BMI, kgm) as a proxy for percentage of body fat (PFat) in longitudinal studies of children and adolescents remains commonplace. Our objective was to test the validity of change in BMI as a proxy for change in PFat measured by dual-energy X-ray absorptiometry (DXA) during adolescence.
Longitudinal study.
Healthy, predominantly Australian youth of mainly Caucasian background (131 females and 115 males) underwent repeated measures at 12.0 (SD 0.3) and 16.0 (SD 0.3) years for height, weight and PFat (DXA).
There was no significant difference in the percentage changes in BMI and PFat for the females (β=2.45, standard error (SE)=1.39, 95% confidence interval (CI)=[-0.27; 5.17]) with their mean BMI increasing 15% as their mean PFat increased 18%. However, for the males, while their mean BMI also increased 15%, their mean PFat was reduced 25%; this change being highly significant (β=-42.25, SE=2.23, 95% CI=[-46.22, -38.27]).
While change in BMI is likely to be a rough proxy for change in PFat measured by DXA in longitudinal studies of adolescent females, this is not the case for adolescent males, where increased BMI is likely to correspond with decreased PFat. Consequently, inferences from longitudinal studies of adolescents which have assumed that an increase in BMI (or BMI Z-scores or percentiles) represents an increase in adiposity require reconsideration.
尽管有证据表明需谨慎行事，但在儿童和青少年的纵向研究中，使用体重指数（BMI，kg/m）作为体脂百分比（PFat）的替代指标仍然很常见。我们的目的是检验在青春期，BMI变化作为双能X线吸收法（DXA）测量的PFat变化的替代指标的有效性。
纵向研究。
健康的、主要为澳大利亚背景的青少年（131名女性和115名男性），主要是白种人，在12.0（标准差0.3）岁和16.0（标准差0.3）岁时对身高、体重和PFat（DXA）进行重复测量。
女性的BMI和PFat百分比变化无显著差异（β=2.45，标准误（SE）=1.39，95%置信区间（CI）=[-0.27；5.17]），其平均BMI增加15%，平均PFat增加18%。然而，对于男性，虽然他们的平均BMI也增加了15%，但他们的平均PFat却减少了25%；这种变化非常显著（β=-42.25，SE=2.23，95%CI=[-46.22，-38.27]）。
在青少年女性的纵向研究中，BMI变化可能大致替代DXA测量的PFat变化，但对于青少年男性并非如此，在青少年男性中，BMI增加可能与PFat减少相对应。因此，那些认为BMI（或BMI Z评分或百分位数）增加代表肥胖增加的青少年纵向研究推论需要重新考虑。
