本文主要目的在介紹身體活動的基本概念，並對身體活動與體重管理的關係進行學術上之闡述。過重與肥胖係指身體囤積過量的脂肪，可能導致各種危害健康的慢性疾病，如糖尿病、心血管疾病和癌症。體重變化取決於能量平衡，亦即是一種個體在攝入與消耗能量間之平衡關係；只要是攝入的食物，都會有熱量囤積的可能、而任何形式的身體活動，包含休息、運動與攝取食物動作，也一定會消耗相當的能量。由於能量消耗與身體活動之間存在著正向且互動關係，規律的身體活動在體重管理議題上就扮演一個重要的角色。根據美國運動醫學學會對成年人身體活動量的建議，每位成年人運動量應達每週至少五天、每次至少30鐘的中等運動強度（或是至少20分鐘的高度運動強度）的身體活動。與國內國民健康局的運動指引比較，國內慣用的333運動指引所推估的運動量似有不足的現象，更遑論套用在特殊需求族群上。套用能量平衡的概念，是一個有效的體重管理方式，瞭解能量攝入與消耗間的關係，將有助我們達成體重管理的目標。此外，動態生活、亦即強調將身體活動融入生活中，即是成功控制體重、有效促進健康的最佳方法。

The purpose of this article is to introduce the basic concept of physical activity, additionally, to describe the relationship between physical activity and weight management. Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health; they also are major risk factors for a number of chronic diseases, such as diabetes, cardiovascular diseases and cancer. Body weight is determined by the number of calories we eat each day minus what our body uses, such mechanism also known as energy balance. Everything we drink or eat contains calories, and every movement we move uses calories, including exercise, sleeping, breathing, and digesting food. Since there is an interactive and positive relationship between physical activity and calories consumption, regular exercise plays an important role on weight management. According to American College of Sport Medicine' recommendation, for the purpose to promote and maintain health, all healthy adults aged 18 to 65 need moderate-intensity aerobic physical activity for a minimum of 30 min on five days each week or vigorous-intensity aerobic physical activity for a minimum of 20 min on three days each week. Compare to the recommendation of 333-exercise-guideline from Bureau of Health Promotion, Taiwan, it seems that the total volume of physical activity is not enough for general population, not to mention the special need population. The effective method to management our weight is energy balance; balancing the number of calories we expend through exercise and physical activity with the calories we eat will help us achieve our health-weight. In addition, the key to successful weight loss and improved overall health is making physical activity a part into our daily routine, that is, the active lifestyle.