Abstract：Obesity is usually associated with common chronic diseases and metabolic syndrome, and lack of physical activity has become the fourth leading risk factor for death from diseases worldwide. For a long time, sufficient exercise has been considered to have many health benefits, and it plays a role in maintaining an ideal body weight. Therefore, the purpose of this study was to understand the relationship between the percentage of the population engaged in regular exercise and changes in body mass index (BMI), through demographic data regarding regular exercise and BMI in Taiwan. Survey data covering 2006 to 2019 from the Sports Administration, Ministry of Education was analyzed to address these questions. The results showed a positive yearly trend in the percentage of population engaging in regular exercise; meanwhile, the percentage of overweight and obese people displays a similarly increasing trend. In contrast, the percentage of individuals of standard or low weight decreased. The percentage of population exercising regularly is positively correlated with the percentage of those obese or overweight, especially in females and the younger population, and negatively correlated with the percentage of those of standard or low weight. In conclusion, there is no indication that regular exercise is beneficial in controlling obesity or excess weight. It is recommended that while engaging in regular exercise, people need to increase exercise intensity or frequency, and monitor their own weight over time to achieve the goal of weight control. (Full text)