The average person requires each day: 2000 for women and 2500 for men.
一个人一天需要摄取的卡路里标准值：女性需要2000卡热量，而男性需要2500卡热量。
Those estimates（估算） are based on factors like average weight, physical activity and muscle mass.
这些是根据平均体重、运动量、和肌肉量估算的。
So does that mean everyone should shoot for around 2000 calories?
所以这意味着每个人都需要摄取大约2000卡的热量吗？
Not necessarily.
并非如此。
If you're doing an energy guzzling（暴饮暴食） activity, like cycling the Tour de France, your body could use up to 9000 calories per day.
如果你做一个高耗能的运动，比如环法自行车赛，你的身体每天可以消耗9000卡的热量。
Pregnancy requires slightly more calories than usual, and elderly people typically have a slower metabolic（新陈代谢的） rate, energy is burned more gradually, so less is needed.
怀孕时会消耗比平常稍微多点的卡路里，而老年人新陈代谢率较低，热量消耗得较慢，所以需要摄取的热量也相对较少。
Here's something else you should know before you start counting calories.
在计算卡路里前，你需要知道以下事项。
The calorie counts on nutrition labels measure how much energy the food contains, not how much energy you can actually get out of it.
营养成分标签上计算的是食物所含的热量，而不是你实际上能摄取到的热量。
Fibrous foods like celery（芹菜） and whole wheat take more energy to digest, so you'd actually wind up with less energy from a 100 calorie serving of celery than a 100 calorie serving of potato chips.
像芹菜和全麦这样的纤维性食物，需要更多的热量去消化。所以，其实你吃100卡的芹菜所摄取的热量会比100卡的洋芋片来得少。
Not to mention the fact that some foods offer nutrients like protein（蛋白质） and vitamins, while others provide far less nutritional value.
更何况有些食物还包含像蛋白质和维他命这样的营养成分；而另一些食物甚至有着较低的营养价值。
Eating too many of those foods could leave you overweight and malnourished.
如果吃太多这些食物，你会营养过剩或营养不良。
And even with the exact same food, different people might not get the same number of calories.
另一方面，即使吃一样的食物，不同的人摄取的卡路里也不同。
Variations in things like enzyme（酶） levels, gut bacteria（肠道细菌）, and even intestine（肠） length, means that every individual's ability to extract（吸收） energy from food is a little different.
因为每个人都有着不同的酵素含量、肠道细菌、甚至是肠子长度。因此，每个人吸收热量的能力也不同。
So a calorie is a useful energy measure, but to work out exactly how many of them each of us requires we need to factor in things like exercise, food type, and our body's ability to process energy.
所以卡路里是个实用的热量计算方式，但要算出每个人所需的热量，我们必须考虑其他因素，比如运动、食物种类以及我们身体的消化能力。
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