The physical behaviour intensity spectrum and body mass index in school-aged youth: A compositional analysis of pooled individual participant data

We examined the compositional associations between the intensity spectrum derived from incremental acceleration intensity bands and the body mass index (BMI) z-score in youth, and investigated the estimated differences in BMI z-score following time reallocations between intensity bands. School-aged...

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Main Authors: Fairclough, Stuart J, Hurter, Liezel, Dumuid, Dorothea, Gába, Ales, Rowlands, Alex V, del Pozo Cruz, Borja, Cox, Ashley, Crotti, Matteo, Foweather, Lawrence, Jones, Owen R, McCann, Debroah A, Noonan, Robert J, Owen, Michael B, Rudd, James Robert, Taylor, Sarah L, Tyler, Richard, Boddy, Lynne M, Graves, Lee E. F
Format: Article
Language:English
Subjects:
accelerometer
adiposity
adolescents
children
CoDa
intensity spectrum
physical activity
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Summary:We examined the compositional associations between the intensity spectrum derived from incremental acceleration intensity bands and the body mass index (BMI) z-score in youth, and investigated the estimated differences in BMI z-score following time reallocations between intensity bands. School-aged youth from 63 schools wore wrist accelerometers, and data of 1453 participants (57.5% girls) were analysed. Nine acceleration intensity bands (range: 0–50 mg to ≥700 mg) were used to generate time-use compositions. Multivariate regression assessed the associations between intensity band compositions and BMI z-scores. Compositional isotemporal substitution estimated the differences in BMI z-score following time reallocations between intensity bands. The ≥700 mg intensity bandwas strongly and inversely associated with BMI z-score (p < 0.001). The estimated differences in BMI z-score when 5 min were reallocated to and from the ≥700 mg band and reallocated equally among the remaining bands were −0.28 and 0.44, respectively (boys), and −0.39 and 1.06, respectively (girls). The time in the ≥700 mg intensity band was significantly associated with BMI z-score, irrespective of sex. When even modest durations of time in this band were reallocated, the asymmetrical estimated differences in BMI z-score were clinically meaningful. The findings highlight the utility of the full physical activity intensity spectrum over a priori-determined absolute intensity cut-point approaches.