This study explored the critical factor involved in producing lifestyle-related diseases. About 2,611 users of public sports facilities, ranging in age from 16 to 79 years, were required to answer a questionnaire about their living habits, psychological stress, physique index and occupations. The data were processed by a principal component analysis and the following findings were obtained. (1) A positive correlation was shown among the three items inquired; lack of meal, nutritional intake status and smoking. These three items formed a main factor of lifestyle-related diseases for both male and female respondents. (2) In case of male respondents, deskwork, as well as lack of exercise, was identified as a risk factor of lifestyle-related diseases such as psychological stress and obesity. (3) For female respondents, drinking and intake of the saturated fatty acid (SFA) and salt composed a main factor of lifestyle-related diseases. (4) In comparison with females with a standard body weight, obese females gave more desirable answers regarding exercise practice and intake of the SFA and salt. These findings indicate that, for males, the lack of exercise and psychological stress are the risk factors inducing lifestyle-related diseases, whereas, for females, drinking and eating are possible risk factors responsible for lifestyle-related diseases. Therefore, this study suggests that, for preventive education of lifestyle-related diseases, it is important to clarify the difference in their behavioral between males and females.