A comparative study of % fat was carried out on Nepali children (Ranging from 6 to 18 years old) to clarify the cause of obesity attended with modernization. 126 males and 79 females who have a natural living style, in rural district (KV) and 166 males and 133 who have a living style affected by the rapid urbanization, in suburban district (BV) were selected as subjects. %Fat was estimated from skinfold thickness according to the method of Nagamine (1975). The results summarized as follows. 1) Mean %Fat of BV in each age were clearly higher than those of KV with coincidental age, especially in male subjects. 2) According to the previous reports (Yoshimizu et al., 1990; Ito et al., 1989), it's considered physical activities in the subjects of BV were lower than those of the subjects in KV. But we could not found the nutritional factors to explain the difference of % fat between BV and KV. From these results, it's considered the difference of % fat in both districts is due to the difference of their physical activities.