Like fat in a fire, the calories in our body generate heat when "burned off" (oxidized), though much more slowly. The "heat" allows us to maintain body temperature at 37 ℃ and allows normal organ and body functions. The measure of the heat is called a "calorie."
油在空氣中燃燒後產生高熱，而在身體內脂肪燃燒（氧化）的速度就慢很多，卻同樣會產生「熱」，讓我們身體維持攝氏卅七度的體溫，也讓我們的器官運動以及肢體活動。