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Longitudinal changes in juvenile and adolescent body mass indices before, during, and after the COVID-19 lockdown in New Zealand.

Floyd, Bruce, Battles, Heather T, White, Sophie, Loch, Carolina, McFarlane, Gina, Guatelli-Steinberg, Debbie, Mahoney, Patrick (2023) Longitudinal changes in juvenile and adolescent body mass indices before, during, and after the COVID-19 lockdown in New Zealand. American journal of human biology : the official journal of the Human Biology Council, 35 (5). Article Number e23861. ISSN 1520-6300. (doi:10.1002/ajhb.23861) (KAR id:99756)


This study uses longitudinal data from school children in Dunedin, New Zealand, to evaluate impacts of COVID-19 lockdown measures on changes in body mass (BMI, kg/m ). Impacts are assessed using two non-mutually exclusive hypotheses. The "structured days" hypothesis holds that children tend to alter sleep patterns, reduce activity and increase snacking when not in structured environments. The bidirectional hypothesis proposes that over-weight or obese children are predisposed to further gains in unstructured settings. Juveniles and adolescents (n = 95, 60% female) were recruited from Dunedin schools. Repeated measures analyses assessed variation in intra-individual change in BMI during four periods: P1 (before summer break), P2 (during summer break), P3 (during the COVID-19 lockdown), and P4 (after the lockdown ended). The model also examined if these changes were influenced by participants' sex or body size early in the first period assessed using log-transformed BMI, log-transformed weight, height, or lower leg length. Repeated measures analyses of per month gains in BMI (kg/m ) during the four periods revealed consistent period (p ≤ .001), period by sex (p ≤ .010), and period by body size (p ≤ .001) interactions across all four body size proxies. Both sexes experienced the greatest gains during the lockdown (P3), but differed in response to their summer break (P2). Results are mostly consistent with the "structured days" hypothesis, but challenge the bidirectional hypothesis as defined. Further research better characterizing risks of gains in adiposity are needed. [Abstract copyright: © 2023 The Authors. American Journal of Human Biology published by Wiley Periodicals LLC.]

Item Type: Article
DOI/Identification number: 10.1002/ajhb.23861
Additional information: For the purpose of open access, the author(s) has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising.
Subjects: G Geography. Anthropology. Recreation > GN Anthropology
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation
Funders: Leverhulme Trust (
SWORD Depositor: JISC Publications Router
Depositing User: JISC Publications Router
Date Deposited: 01 Feb 2023 15:19 UTC
Last Modified: 12 Dec 2023 12:27 UTC
Resource URI: (The current URI for this page, for reference purposes)

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