Degree of Accuracy of the BMI Z-Score to Determine Excess Fat Mass Using DXA in Children and Adolescents

David Monasor-Ortolá, Jose Antonio Quesada-Rico, Ana Pilar Nso-Roca, Mercedes Rizo-Baeza, Ernesto Cortés-Castell, Asier Martínez-Segura and Francisco Sánchez-Ferrer
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David Monasor-Ortolá: Department of Nursing, University of Alicante, 03690 Alicante, Spain
Jose Antonio Quesada-Rico: Department of Clinical Medicine, Miguel Hernández University of Elche, 03550 Elche, Spain
Ana Pilar Nso-Roca: Department of Pharmacology, Pediatrics and Organic Chemistry, Miguel Hernández University of Elche, 03550 Elche, Spain
Mercedes Rizo-Baeza: Department of Nursing, University of Alicante, 03690 Alicante, Spain
Ernesto Cortés-Castell: Department of Pharmacology, Pediatrics and Organic Chemistry, Miguel Hernández University of Elche, 03550 Elche, Spain
Asier Martínez-Segura: Department of Nursing, University of Alicante, 03690 Alicante, Spain
Francisco Sánchez-Ferrer: Department of Pharmacology, Pediatrics and Organic Chemistry, Miguel Hernández University of Elche, 03550 Elche, Spain

IJERPH, 2021, vol. 18, issue 22, 1-9

Abstract: Obesity is caused by fat accumulation. BMI Z-score is used to classify the different degrees of weight status in children and adolescents. However, this parameter does not always express the true percentage of body fat. Our objective was to determine the degree of agreement between the fat mass percentage measured by DXA and the stratification of weight according to BMI Z-score in the pediatric age group. We designed a descriptive cross-sectional study. The patients were classified as underweight/normal weight with Z-scores between ?2 and +0.99, overweight from 1 to 1.99, obese from 2 to 2.99, and very obese ?3. We included 551 patients (47% girls), with a mean age of 11.5 ± 2.8 years (3.7–18 years). Higher BMI Z-scores were associated with a higher percentage of total fat ( p < 0.001). However, there were important overlaps between both parameters, such that the BMI Z-score classified patients with the same percentage of total fat mass as having a different nutritional status classification. In conclusion, the stratification of weight status according to BMI Z-score revealed that 46.7% of patients had a fat percentage that did not correspond to their classification. For a more accurate weight assessment in clinical practice, we recommend combining anthropometric indices with diagnostic tools that better correlate with DXA, such as electrical bioimpedance.

Keywords: BMI Z-score; childhood obesity; body composition; fat mass; growth charts (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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