To provide basis for health-related physical curriculum reform and health education in primary and secondary schools.

In September 2018, a total of 23 191 students from grades 1 to 12 in Chengdu were selected for a physical fitness test using a stratified random cluster sampling method. Additionally, 1 024 middle school students from grades 7, 8, 10, and 11 were randomly selected for a lifestyle questionnaire survey. Rank correlation analysis was employed to compare the differences in physical fitness among students with different BMI levels, and linear correlation analysis was used to examine the associations between physical fitness and lifestyle factors such as diet, exercise, and sleep.

The respondents’ sit-and-reach test scores (r_s=0.042, P=0.009), grip strength (r_s=0.499, P<0.001) increased with BMI level, while the vital capacity body mass index decreased with BMI level (r_s=-0.242, P<0.001). With increasing BMI levels, the physical comprehensive scores of the respondents tended to increase at first and then decrease. Using BMI as the independent variable and physical comprehensive score as the dependent variable, a total of eight regression equations were derived. As follows: Grades 3-4: male students: y=-0.016X²+0.423X-2.532, female students: y=-0.005X²+0.123X-0.588; Grades 5-6: male students: y=-0.027X²+0.841X-6.214, female students: y=-0.012X²+0.314X-1.741; Grades 7-9: male students: y=-0.038X²+1.521X-14.666, female students: y=-0.008X²+0.163X-0.132; Grades 10-12: male students: y=-0.035X²+1.428X-14.233, female students: y=0.007X²-0.390X+5.160. The pass rates of the surveyed subjects in the standing long jump (r=0.567, P<0.001) and visual acuity (r=0.425, P<0.001) were positively correlated with exercise. The vital capacity body mass index pass rate for male students(r=0.504, P=0.028) was positively correlated with exercise. The BMI pass rate for female students was positively correlated with both diet (r=0.688, P=0.017) and exercise (r=0.497, P=0.012).

Middle school students’ vital capacity body mass index, standing long jump, and visual acuity status were related to exercise. Female students’ BMI was related to diet. The physical fitness, BMI, and lifestyle of primary and middle school students are mutual influence, mutual cause and effect.