Physical activity is a key factor for preventing and improving metabolic syndrome. Herein, we examined the relationship between physical activity levels and health-related factors in middle-aged men and women with a high prevalence of metabolic syndrome. The subjects were 963 men and women aged 40 to 64 (638 men, 325 women) who underwent health checkups at Mine City Hospital and completed a lifestyle questionnaire. Subjects were classified into four groups based on physical activity levels: Level 1, < 120 METs·min/week (n = 303); Level 2, 120 to < 1380 METs·min/week (n = 323); Level 3, 1380 to < 3600 METs·min/week (n = 190); and Level 4, ≥ 3600 METs·min/week (n = 147). We analyzed metabolic syndrome diagnosis results; physical characteristics; blood pressure; blood test values; daily inactive time, excluding sleep duration; dietary literacy; obesity-prone eating behaviors; social networks (LSNS-6); sleep status (AIS); and psychological state (K6). We found that physical activity levels of Level 2 or higher were associated with a lower prevalence of metabolic syndrome. Increasing physical activity levels were associated with reduced inactive time, higher dietary literacy scores, increased social network scores, and higher HDL cholesterol levels. Individuals with low physical activity levels had lower dietary literacy, suggesting an increased risk of metabolic syndrome development, and tended to have weaker social networks.