A cross-sectional study of lifestyle factors related to body mass index, skeletal muscle mass, and skeletal muscle index in male Japanese workers

The study was a cross-sectional study of 377 male Japanese workers to investigate the relationship between lifestyle habits and body composition components, such as body mass index (BMI), grip strength, skeletal muscle mass, and skeletal muscle index (SMI), to promote the prevention of sarcopenic obesity and sarcopenia. Their sleep quality was evaluated using the Athens Insomnia Scale (AIS), and their exercise habits were assessed using the Japanese version of the International Physical Activity Questionnaire. Body composition components, including body fat mass and skeletal muscle mass, were measured using a body composition impedance analyzer, InBody470. Handgrip strength and SMI were evaluated based on the standard values set in the Asian Working Group for Sarcopenia 2019 (AWGS 2019) guidelines. Of the 377 participants, 119 (31. 6%) had a BMI of ≥25. 0 kg/m². According to the AWGS 2019 guidelines, these participants did not meet the criteria for sarcopenic obesity. Participants with a higher BMI had higher age and handgrip strength (trend, P < 0. 001). Additionally, they had higher skeletal muscle mass and SMI (trend, P < 0. 001). Multiple regression analysis was performed using skeletal muscle mass and SMI as dependent variables, which revealed that skeletal muscle mass and SMI were associated with age, BMI, breakfast intake, and waist circumference. Furthermore, skeletal muscle mass was associated with heavy physical activity. From the perspective of disease prevention, our findings highlight the importance of prioritizing breakfast intake and physical activity to maintain muscle mass.