What is fat? - George Zaidan

什么是脂肪？- George Zaidan

Translator: Andrea McDonough Reviewer: Jessica Ruby

翻译人员: Peipei Xiang 校对人员: Yixuan Liu

Olive oil is 100% fat;

橄榄油含有100%的脂肪，

there's nothing else in it.

除此之外没有别的。

Pancake mix, on the other hand,

相反，煎饼

is only about 11% fat.

只有约11%的脂肪，

And, yet, olive oil is good for you,

然而，橄榄油对你的身体有益，

and pancake mix is not.

煎饼则不然。

Why is that?

为什么会这样呢？

As it turns out,

原来，

the amount of fat we eat

我们摄入的脂肪含量

doesn't impact our weight

并不影响我们的体重，

or our cholesterol

或我们的胆固醇，

or our risk of heart disease

或我们得心脏病的机率，

nearly as much as what kind of fat we eat.

而这些只是跟我们摄入的脂肪种类有关。

But let's back up:

不过我们先回过头来：

What is fat?

什么是脂肪？

If we were to zoom in on a salmon,

如果我们把三文鱼放大来看，

which is a fatty fish,

三文鱼是一种脂肪很多的鱼，

past the organs,

past the tissues,

不看内脏，

不看组织，

into the cells,

只看细胞，

we would see that the stuff we call fat

我们就会看到我们称之为脂肪的东西

is actually made up of molecules called triglycerides,

其实是是由一种叫三酸甘油酯的分子所组成的，

and they are not all alike.

而这些分子并不完全相似。

Here's one example.

这里举一个例子。

Those three carbons on the left, that's glycerol.

左边的那三颗碳，是甘油，

Now, you can think of that as the backbone

你可以把它想像成骨干，

that holds the rest of the molecule together.

它能够把其它的分子紧紧连在一起。

The three long chains on the right

右边的那三条长链

are called fatty acids,

被称为脂肪酸，

and it's subtle differences in the structures of these chains

这些分子链结构的微妙差别

that determine whether a fat is,

决定了某种脂肪

let's say, solid or liquid;

比如说，是固体的还是液体的，

whether or not it goes rancid quickly;

是否会很快变质，

and, most importantly, how good or how bad it is for you.

最重要的是，对你是有益的还是有害的。

Let's take a look at some of these differences.

让我们来看看这些差别。

One is length.

一个是长度，

Fatty acids can be short or long.

脂肪酸可长可短。

Another, more important difference

另一个更重要的区别是

is the type of bond between the carbon atoms.

连接碳原子的碳键的形式。

Some fatty acids have only single bonds.

有些脂肪酸只有单键，

Others have both single and double bonds.

另外一些则同时拥有单键和双键。

Fatty acids with only single bonds

只有单键的脂肪酸

are called saturated,

为饱和脂肪酸，

and those with one or more double bonds

有单个或多个双键的脂肪酸

are called unsaturated.

则为不饱和脂肪酸。

Now, most unsaturated fats are good for you,

大部分的不饱和脂肪酸对人体是有益的，

while saturated fats are bad for you in excess.

而过多的饱和脂肪酸则是有害的。

For saturated fats, the story pretty much ends there

就饱和脂肪酸而言，基本上就是这样。

but not for unsaturated fats.

就不饱和脂肪酸而言，

The double bonds in these molecules

双键在这些分子中

have a kind of weird property;

有一种奇怪的特性，

they're rigid.

它们有十分坚固的刚性结构。

So, that means there are two ways

这意味着有两种

to arrange every double bond.

排列组合双键的方式。

The first is like this,

第一种就像这样，

where both hydrogens are on same side

两颗氢都在同一边，

and both carbons are on the same side.

两颗碳也在同一边。

The second way is like this.

第二种方式像这样，

Now the hydrogens and carbons

氢和碳

are on opposite sides of the double bond.

在双键对立的两端。

Now, even though both of these molecules

尽管这两种分子

are made up of exactly the same building blocks,

由一模一样的东西组成，

they are two completely different substances,

它们是完全不同的物质，

and they behave completely differently inside of us.

在我们体内也表现得完全不同。

The configuration on the left is called CIS,

左边的这个结构称为顺式异构体 (CIS)，

which you've probably never heard of.

你可能从来也没听过。

The one of the right is called TRANS,

右边的这个称为反式异构体 (TRANS)，

and you probably have heard of trans fats before.

你以前可能有听过反式脂肪，

They don't go rancid,

它们不容易变质，

they're more stable during deep frying,

它们在油炸时比较稳定，

and they can change the texture of foods

而且它们可以改变食物的口感，

in ways that other fats just can't.

这是其它种类的脂肪无法做到的。

They're also terrible for your health,

但是它们非常不益健康，

by far worse than saturated fat,

比饱和脂肪还要坏，

even though technically they're a type

虽然严格来说，它们是不饱和脂肪的一种。

of unsaturated fat.

虽然严格来说，它们是不饱和脂肪的一种。

Now, I know that seems crazy,

我知道，这听上去很不可思议，

but your body doesn't care

但是你的身体可不管

what a molecule looks like on paper.

某个分子在纸上的样子，

All that matters is the 3-D shape

它只在乎它们的立体形状，

where the molecule fits,

分子在哪里结合，

where it doesn't,

哪里不结合，

and what pathways it interferes with.

还有它所经之处造成的影响。

So, how do you know if a food

那么，你怎么知道一种食物

has trans fat in it?

是否还有反式脂肪呢？

Well, the only sure way to know

唯一能够确定的方法是

is if you see the words,

看食品成分里面有没有「 部分氢化」的字眼。

"partially hydrogenated" in the ingredients list.

看食品成分里面有没有「 部分氢化」的字眼。

Don't let nutrition labels or advertising fool you.

别让营养标签或广告骗了你。

The FDA allows manufacturers to claim

美国食品药物管理局 (FDA) 允许制造商宣称

that their products contain

他们的产品包含

"0" grams of trans fat

「0」克的反式脂肪，

even if they actually have up to half a gram per serving.

即使“每份”的反式脂肪含量多达 0.5 克（低于0.5克）。

But there are no hard and fast rules

但是没有严格的规定

about how small a serving can be,

限制“每份”最少应该是多少，

and, that means, you'll have to rely on seeing those key words,

这就意味着，你得依赖关键字——

partially hydrogenated,

「 部分氢化」，

because that's how trans fats are made,

因为那是制造反式脂肪的方式，

by partially hydrogenating unsaturated fats.

即透过部份氢化不饱和脂肪。

So, let's go back to our olive oil and pancake mix from before.

那我们再回到我们之前提到的橄榄油和煎饼。

Olive oil is 100% fat.

橄榄油是 100% 的脂肪，

Pancake mix is only 11% fat.

煎饼只有约11%的脂肪。

But olive oil is mostly unsaturated fat,

但是橄榄油含得大部分式不饱和脂肪，

and it has no trans fat at all.

完全不含反式脂肪。

On the other hand, more than half the fat

然而，煎饼里面超过一半的脂肪是

in pancake mix is either saturated or trans fat.

饱和脂肪或反式脂肪。

And, so, even though olive oil has 10 times

所以，虽然橄榄油含的脂肪是煎饼的10倍，

as much fat as pancake mix,

it's healthy for you,

它对你是有益的，

whereas pancake mix is not.

而煎饼则不然。

Now, I'm not trying to pick on pancake mix.

当然我并不是要故意针对煎饼。

There are lots of foods

有很多的食品

with this type of fat profile.

含有这种类型的脂肪。

The point is this:

重点是：

It's not how much fat you eat,

吃多少脂肪不重要，

it's what kind of fat.

而是你吃了什么样的脂肪。

And what makes a particular fat healthy or unhealthy

决定一种脂肪是否健康的关键

is its shape.

是它的形状。