Cardiorespiratory fitness and body mass index on metabolic syndrome in middle-aged Japanese adults under national health guidance: a cross-sectional study oleh Xiangyu Zhai, Susumu S. Sawada, Sayaka Kurosawa, Sakura Koriyama, Serena A. Dimitroff, Shinji Sato, Yuko Oguma, Yoshio Nakata, Kazushi Maruo, Motohiko Miyachi, Yuko Gando, Koichiro Oka, Duck-chul Lee