The reciprocal relationship between body mass index categories and physical fitness: A 4-year prospective cohort study of 20 000 Chinese children

摘要

Introduction Body mass index (BMI) categories and physical fitness are associated but the reciprocal relationship between BMI categories and physical fitness has not been investigated. This study aims to investigate the longitudinal reciprocal relationship between BMI categories and physical fitness. Methods This is a population‐based 4‐year cohort study in 48 elementary schools. Children aged 6 to 9?years at recruitment were included. BMI categories and physical fitness including handgrip strength, core muscle endurance, flexibility, and cardiorespiratory fitness were measured using standard equipment and protocol. Results Among 26?392 eligible participants, 19?504 (73.9%) were successfully followed for 3?years. Baseline obesity prevalence was 5.9%. After 3?years, those who were unfit at baseline had an increased risk of obesity (risk ratio [RR] 1.41, 95% CI 1.16‐1.71, P