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. 2019 Jan;43(1):82-90.
doi: 10.1038/s41366-018-0183-1. Epub 2018 Sep 4.

BMI does not capture the high fat mass index and low fat-free mass index in children with cerebral palsy and proposed statistical models that improve this accuracy

Daniel G Whitney  1 , Freeman Miller  2 , Ryan T Pohlig  3 , Christopher M Modlesky  4
Affiliations

BMI does not capture the high fat mass index and low fat-free mass index in children with cerebral palsy and proposed statistical models that improve this accuracy

Daniel G Whitney et al. Int J Obes (Lond). 2019 Jan.

Abstract

Background/objectives: Children with cerebral palsy (CP) are at risk for having a misclassified overweight/obesity status based on BMI thresholds due to their lower fat-free mass and similar fat mass compared with typically developing children. The primary objective was to determine if BMI could predict fat mass index (FMI) and fat-free mass index (FFMI) in children with CP.

Subjects/methods: Forty-two children with CP and 42 typically developing children matched to children with CP for age and sex participated in the study. Dual-energy X-ray absorptiometry was used to assess body composition. Children with CP who could ambulate without assistance were considered ambulatory (ACP) and the rest were considered nonambulatory (NACP).

Results: Children with CP had higher percent body fat (%Fat) and FMI and lower fat-free mass and FFMI than controls (p < 0.05) but no difference in fat mass (p = 0.10). When BMI was statistically controlled, NACP had higher %Fat, fat mass and FMI and lower FFMI than ACP and controls (p < 0.05). NACP also had lower fat-free mass than controls (p < 0.05). ACP had higher %Fat and FMI and lower fat-free mass and FFMI than controls (p < 0.05). BMI was a strong predictor of FMI (r2 = 0.83) and a moderately strong predictor of FFMI (r2 = 0.49) in children with CP (both p < 0.01). Prediction of FMI (R2 = 0.86) and FFMI (R2 = 0.66) from BMI increased (p < 0.05) when age, sex and ambulatory status were included.

Conclusion: Compared with typically developing children, children with CP have a higher FMI and lower FFMI for a given BMI, which is more pronounced in NACP than ACP. The finding suggests that the prevalence of overweight/obesity status may be underestimated in children with CP.

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Conflict of interest statement

Conflict of Interest

All authors declare no conflict of interest.

Figures

Figure 1.
Figure 1.
Bar graphs represent (A) body mass index (BMI), (B) fat mass index (FMI) statistically controlled for BMI and (C) fat-free mass index (FFMI) statistically controlled for BMI for nonambulatory children with cerebral palsy (NACP), ambulatory children with CP (ACP) and typically developing children (Con). Values are means ± SE. *Different from controls, p < 0.05. †Different from ACP, p < 0.05.
Figure 2.
Figure 2.
Scatter plot demonstrating (A) the relationships between body mass index (BMI) and fat mass index (FMI) and (B) the relationships between BMI and fat-free mass index (FFMI) in children with cerebral palsy (CP) and typically developing children (Con).
Figure 3.
Figure 3.
Scatter plot comparing the measured values to the estimated values of (A) fat mass index (FMI) and (B) fat-free mass index (FFMI) in children with cerebral palsy (CP) using multiple linear regression and body mass index, age, sex and ambulatory status and the models shown in Table 3. The dotted diagonal line represents the line of identity.
See this image and copyright information in PMC

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