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

Summary 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....