What is a calorie? - Emma Bryce

譯者: Harry Chen 審譯者: Bethany Zhang

We hear about calories all the time.

我們不時聽到「卡路里」

How many calories are in this cookie?

這個餅乾裡有多少卡路里呢？

How many are burned by 100 jumping jacks,

做 100 個開合跳、長跑或是仰臥起坐 會燃燒掉多少卡路里呢？

or long distance running,

or fidgeting?

But what is a calorie, really, and how many of them do we actually need?

可是 1 卡路里究竟代表什麼呢？ 還有我們實際上需要多少卡路里呢？

Calories are a way of keeping track of the body's energy budget.

卡路里是一種監測人體能量 消耗量的方法

A healthy balance occurs when we put in about as much energy as we lose.

當我們攝入的能量和消耗的能量相同， 就是一種較為健康的平衡。

If we consistently put more energy into our bodies than we burn,

可是，如果我們不斷地攝入比我們 所燃燒的能量還要多的時候

the excess will gradually be stored as fat in our cells,

多出來的能量將會逐漸地被當作 脂肪儲存在我們的細胞裡

and we'll gain weight.

導致體重增加

If we burn off more energy than we replenish, we'll lose weight.

相反，如果我們消耗的能量超過 攝入的能量，體重就會減輕

So we have to be able to measure the energy we consume and use,

所以我們需要一種方法量化 我們所攝入和消耗的能量

and we do so with a unit called the calorie.

於是，我們引入「卡路里」這個概念

One calorie, the kind we measure in food, also called a large calorie,

用於量化食物所含熱量， 1 千卡路里又叫做 1 大卡

is defined as the amount of energy

其定義為：1 公升的水

it would take to raise the temperature of one kilogram of water

by one degree Celsius.

溫度升高一攝氏度所需要的能量

Everything we consume has a calorie count,

我們吃進去的所有食物有卡路里值，

a measure of how much energy the item stores in its chemical bonds.

它指的是破壞食物分子中的 化學鍵所需的能量

The average pizza slice has 272 calories,

一片普通大小的披薩切片有 272 大卡

there are about 78 in a piece of bread,

一片土司大概有 78 大卡

and an apple has about 52.

一顆蘋果有 52 大卡

That energy is released during digestion,

這些能量在消化時被釋放出來， 並儲存在分子中。

and stored in other molecules

當人體需要能量時，

that can be broken down to provide energy when the body needs it.

分子就會釋放其中的能量。

It's used in three ways:

能量可用在三個方面：

about 10% enables digestion,

其中10%用於消化；

about 20% fuels physical activity,

20%用於日常活動

and the biggest chunk, around 70%,

剩餘最多的70%用於維持 體內器官和組織的基本運作

supports the basic functions of our organs and tissues.

That third usage corresponds to your basal metabolic rate,

第三種用途與你的基礎代謝率有關

a number of calories you would need to survive

假使你不吃不動

if you weren't eating or moving around.

還是需要這些能量維持生命體征

Add in some physical activity and digestion,

根據官方指南，

and you arrive at the official guidelines

加上日常活動和消化過程，

for how many calories the average person requires each day:

一般人每人每天所需的平均能量為：

2000 for women and 2500 for men.

女性 2,000 大卡；男性 2,500 大卡

Those estimates are based on factors

這些數據是基於人的平均重量、 活動量、肌肉量等要素計算得出。

like average weight, physical activity and muscle mass.

So does that mean everyone should shoot for around 2000 calories?

但這是不是就意味著，每個人 都應該攝入 2,000 大卡左右的卡路里數呢？

Not necessarily.

不必然啦！

If you're doing an energy guzzling activity,

要是我們進行高耗能活動

like cycling the Tour de France,

像是「環法自行車賽」

your body could use up to 9000 calories per day.

那麼一天所需要的能量就有 9,000 大卡

Pregnancy requires slightly more calories than usual,

懷孕需要比平常稍多一些的卡路里

and elderly people typically have a slower metabolic rate,

而年長者通常有比較緩慢的基礎代謝率

energy is burned more gradually, so less is needed.

能量的燃燒會更平緩 因此所需要的是比較少的卡路里

Here's something else you should know before you start counting calories.

開始計算卡路里前 你需要知道一些東西

The calorie counts on nutrition labels measure how much energy the food contains,

營養標示中的卡路里值表示 食物含有了多少能量

not how much energy you can actually get out of it.

而不是你實際上可以 從中得到多少能量

Fibrous foods like celery and whole wheat take more energy to digest,

芹菜和全麥等富含膳食纖維的食物 要用上更多的能量來消化

so you'd actually wind up with less energy from a 100 calorie serving of celery

所以實際上比起享用 100 大卡的洋芋片

享用 100 大卡的芹菜 你會獲得較少的能量做結

than a 100 calorie serving of potato chips.

Not to mention the fact that some foods offer nutrients like protein and vitamins,

更別提事實有些食物供應了像是 蛋白質與維他命等營養

while others provide far less nutritional value.

際此同時其他的食物提供 遠遠較低的營養價值

Eating too many of those foods

吃太多那些低營養的食物

could leave you overweight and malnourished.

只會讓你超重和營養不良

And even with the exact same food,

即便食用完全相同的食物

different people might not get the same number of calories.

不同之人也不會攝入 相同的能量

Variations in things like enzyme levels,

人體內酶水平，腸道細菌甚至是腸道長度差異

gut bacteria,

and even intestine length,

means that every individual's ability to extract energy from food

is a little different.

So a calorie is a useful energy measure,

在計算能量時，卡路里值確實很重要，

but to work out exactly how many of them each of us requires

但是要計算出我們每個人 到底需要多少卡路里

we need to factor in things like exercise,

就應該同時考慮運動量、食物種類

food type,

and our body's ability to process energy.

以及身體處理能量的能力等因素。

Good luck finding all of that on a nutrition label.

祝你幸運地在營養標示上 找到所有這一切的東西！