The purpose of this study was to inform teachers or researchers relating teaching boys and girls of basic data for valid obesity education. The researcher collected 10 students(5 boys and 5 girls) and measured skinfold thickness and body-fat-percentile(% body fat) on 3 parts of the body every month during a year. The researcher checked the spring(March), summer(July), autumn(October) and winter(January) data consecutively and tried to answer the question that which season especially need the preventive education of obesity. The result as followed ; 1. The skinfold and BFP in summer were more bigger than those in winter but these differences were not significant. 2. Girls have a propensity to get higher skinfold and BFP than boys but these differences were not significant neither. Briefly speaking, in 12 months, the skinfold and BFP(compared in summer) in winter season has the highest and it showed that it was necessary to teach students to preserve their appropriate body fat through diverse activities. The researcher expects successive studies for much more students and by type of students are executed for supporting these results.