The objective of this study was to examine the effects of health-related knowledge and aerobic exercise on lower secondary school students' obesity awareness and physical activity levels. A total of 50 obese and 20 normal-weight female students, ranging in age from 12-14 (mean 12.10±1.7), participated in the study. Obesity awareness was determined using the Obesity Awareness Scale, which also incorporates awareness of nutrition and physical activity. Physical activity levels were determined using a pedometer. The participants were divided into one obese experimental group and 2 control groups, obese and normal weight. The obese experimental group received instruction in health and nutrition and followed an aerobic exercise program, while the control groups received no such instruction and did not participate in an exercise program. The health education program was conducted once a week, while the aerobic exercise program was performed three times a week, with each session lasting 45-60 minutes. At the conclusion of the study, the obesity awareness, nutrition awareness, and physical activity awareness scores of the students in the obese experimental group increased significantly compared to those of the obese control and normal control groups. Similarly, the physical activity levels of the students in the obese control group increased with respect to those of the obese and normal-weight control groups. These findings suggest that health-related knowledge and aerobic exercise were effective in increasing obesity awareness and the physical activity levels of lower secondary school students.