Choose the MAIN IDEA from the sentences below. The other sentences will be supporting details that support the main idea. 1. Just one hour of physical activity per week caused a.31 level reduction in Body Mass Index (BMI) for overweight elementary school girls. 2. Ten percent of kindergarten girls are overweight, but that percentage would decline to 5.8% with at least five hours of physical activity per week. 18 3. Recent studies have shown that first graders who had at least three gym classes during the week were less likely to become overweight. 4. Parents and school administrators can successfully prevent childhood obesity by incorporating daily physical activity into their children's lives.