【英语时差8，16】Don的午饭热量

 Ever wonder how they determine how many calories are in food? Yael and Don explain it in this Moment of Science.   Y: All right, Don. What are you doing?

D: I'm using a bomb calorimeter to figure out how many calories are in my lunch. See, I put my sandwich in this sealed container, which I'm going to submerge in water, and then I'm going to burn my sandwich and figure out how much the temperature of the water has changed, because a calorie is defined as the amount of energy it takes to heat up a kilogram of water one degree centigrade--and then--Y: Whoa, Don, two things: First of all, you won't be able to eat your lunch once you burned it.

D: Oh, good point.

Y: Second, no one uses the bomb calorimeter anymore to measure the calorie content of food.

D: They don't?

Y: Nope. Today most of the nutritional¹ information you find on food labels is generated indirectly², using what's known as the Atwater system. So basically, calories are calculated by adding up the calories provided by each of the food's energy- containing nutrients³.

D: Oh, like proteins and fats?

Y: And carbohydrates⁴ and alcohol. According to the Atwater system, there are on average four calories in each gram of protein, nine in each gram of fat, seven in each gram of alcohol, and four in each gram of carbohydrates.

D: Oh, I've seen that conversion⁵ scale on the label on my potato chips.

Y: Also, because some carbs contain fiber⁶ that your body can't break down, their total is adjusted accordingly before figuring out calories. Atwater already figured all that out using your beloved bomb calorimeter, so now you don't have to.

D: Darn. I sure do love burning things!   

1 nutritional   

adj.营养的，滋养的

参考例句：

• A diet lacking in nutritional value will not keep a person healthy.缺乏营养价值的饮食不能维持人的健康。
• The labels on food products give a lot of information about their nutritional content.食品上的标签提供很多关于营养成分的信息。

2 indirectly   

adv.间接地，不直接了当地

参考例句：

• I heard the news indirectly.这消息我是间接听来的。
• They were approached indirectly through an intermediary.通过一位中间人，他们进行了间接接触。

3 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

4 carbohydrates   

n.碳水化合物，糖类( carbohydrate的名词复数 )；淀粉质或糖类食物

参考例句：

• The plant uses the carbohydrates to make cellulose. 植物用碳水化合物制造纤维素。 来自《简明英汉词典》
• All carbohydrates originate from plants. 所有的碳水化合物均来自植物。 来自辞典例句

5 conversion   

n.转化，转换，转变

参考例句：

• He underwent quite a conversion.他彻底变了。
• Waste conversion is a part of the production process.废物处理是生产过程的一个组成部分。

6 fiber   

n.纤维，纤维质

参考例句：

• The basic structural unit of yarn is the fiber.纤维是纱的基本结构单元。
• The material must be free of fiber clumps.这种材料必须无纤维块。