Effects of body size and body fatness on left ventricular mass in children and adolescents: Project HeartBeat!
BACKGROUND
Left ventricular mass (LVM) is a strong predictor of cardiovascular disease in adults. Available study findings on effects of body fatness on LVM in children are inconsistent. Understanding the impact of body fat on LVM in children may help prevent excessive LVM through measures to reduce overweight and obesity.


METHODS
Healthy children (n=678) aged 8, 11, and 14 years at baseline were examined at 4-month intervals for up to 4 years (1991-1995); 4608 valid measurements of LVM were obtained with M-mode echocardiography. A multilevel linear model was used for analysis. The impact of body size was examined by adding separately nine body-size indicators to a basic LVM-gender-age model. The impact of body fatness was tested by introducing four body-fatness indicators into the nine models, yielding 36 models.


RESULTS
All body-size indicators showed strong, positive effects on LVM. In models containing weight or body surface area (measuring both fat-free and fat contributions to body size), additional effects of body fatness were negative; in models containing fat-free mass (FFM) or height (both measuring body size independent of body fat), increased body fatness was related to a significant increase in LVM. For example, in models with FFM as a body-size indicator, a 1-SD increase in percent body fat or fat mass was related to a 5.4- or 7.2-g increase in LVM, respectively.


CONCLUSIONS
Effects of body size on LVM attributable to fat-free body mass can be distinguished from those attributable to fat body mass; both are independent, positive predictors, but the former is the stronger determinant. When a body-size indicator not independent of body fat is used as a predictor, effects of fat-free body mass and fat body mass are forced to relate to the same indicator; because their magnitudes are estimated to be equal, the effect of fat body mass is overestimated. Thus, when an additional body-fatness indicator is included in the prediction of LVM, the additional estimated effect related to the indicator appears to be negative.
Dai
Shifan
S
Division for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, CDC, 4770 Buford Highway NE, Atlanta, GA 30341-3724, USA. sdai@cdc.gov
Harrist
Ronald B
RB
Rosenthal
Geoffrey L
GL
Labarthe
Darwin R
DR
D000273:Adipose Tissue / Q000502:physiology*; D000293:Adolescent; D000367:Age Factors; D050218:Body Fat Distribution; D049628:Body Size / Q000502:physiology*; D002648:Child; D004452:Echocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D012737:Sex Factors