On TV commercials, you sometimes see low calorie food. 在电视广告上，你有时能看到低热量食品。

　　What is a calorie? 什么是卡路里？

　　A calorie is the unit of energy in food. 卡路里是食物中的热量单位。

　　Most food produces energy in your body, but high calorie food is not always good for your health. 大部分食物在你体内产生热量，但高热量食物并不总是对你的健康有益。

　　You don't need a lot of calories a day. 你一天不需要太多的热量。

　　So when you eat more food than you need to, the unused calories are saved in your body. 所以当你吃的食物多于你的所需时，多余的热量就会储存在你的体里。

　　Fast food like pizzas, hamburgers or French fries usually has a lot of calories. 披萨、汉堡或炸薯条之类的快餐有很多卡路里。

　　So you get fat if you always eat fast food. 所以你总吃快餐的话容易变胖。