Obesity and its consequences, affected by modern sedentary life style, are growing constantly. Numerous researches in the Western World countries have illustrated the influences of city form on the physical activity rate and subsequently on health status and body fitness of populations. In spite of the fact that the Iranians obesity rate is not at significant variance with the west countries, there is no specific research engaged with the impact of formal and spatial features of built environment on the residents’ health. Accordingly and with regard to homogeneity in socio-economic factors of population and significant difference between different parts of city, Hashtgerd is appropriate case for the research purpose. In the research, first, 9 residential clusters in different part of the city were selected in which other information (socio-demographic, health status, body fitness and weekly amount of physical activity) were gathered. Statistical society was composed of men and women (parents of the family) with 20 to 50 years old who were selected through the cluster random sampling. The number of cases was derived through the Cochran sampling formula. After that, by investigating regression between different built environment features of the clusters (derived from expert view) and body fitness rate in one hand and residents’ weekly amount of physical activity in the other hand, a list of formal- spatial factors which have effect on amount of physical activity and consequently on health were derived. This list became more completed through deep interviews we had had with the residents. In addition to this a questionnaire (barrier questionnaire) prepared to discover the barriers of walking through the residents’ mind. In the other word, we also wanted to derive the attribute of the built environment which are effective on walking, perceptually. In this questionnaire residents were asked to mention the walking barrier for different kind of travel. The factors were a wide range of formal- spatial features which had to be arranged. After test retest exam which had done to estimate the validity and reliability of the factors, the multivariate linear regression was done between the derived factors from the previous steps and residents’ weakly amount of physical activity. Finally, we concluded that the distance from home to the work place and market centers has the most impact on the walking rate of families. The other crucial factors are safety and diversity of users and functions of space, that the former have a very strong impact on walking of women and the later on the men. The study also showed that extreme climatic and environmental factors have significant adverse impacts on walkability. Appropriate slope for walking, protection from extreme sunshine, rain, wind, etc. can be achieved through appropriate design ideas in order to enhance the quality of the pathways and eventually attract more pedestrians into urban spaces.