OBJECTIVE: The study aims to explore the relationship between modifiable lifestyle factors (physical activity, sedentary time, body composition, muscle strength) and mental health, and predict future changes in mental health. METHODS: A cross-sectional survey was conducted on 133 men (age: 29.03 ± 6.605 years, BMI: 23.58 ± 2.688 kg/m²) to assess baseline body composition, muscle strength, sedentary time, and mental health, with follow-up at 3 months. F-tests were employed to compare the differences in mental health on sedentary time and body composition variables. Spearman correlation analysis was used to examine correlations between variables. RESULTS: Spearman's correlation analysis showed that sedentary time, muscle strength and mental health of the subjects were significantly correlated. BMI, BFM, BFMI, PBF were higher in subjects with ≥ 4 h of sedentary time than in the other two shorter sedentary time groups. Subjects with higher PBF (p = 0.047, η = 0.030) and BFM (p = 0.032, η = 0.035) had severer depression. Subjects who sat for ≥ 4 h at a time were more severely depressed than those who sat for 2-4 h (p = 0.020). Change in depression was significantly negatively correlated with BMI, BFM, BFMI and PBF. Subjects with higher PBF (p = 0.023, η = 0.050) and BFM (p = 0.005, η = 0.075) at the baseline had less change in depression. CONCLUSION: A Significant correlation was found between sedentary time, body composition and mental health, and baseline body composition predicted changes in mood three months later.