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Fat has a reputation in the U.S.
脂肪在美国算是臭大街了。
There's a multi-billion dollar industry dedicated to convincing you to spend a bunch of money to get rid of fat.
甚至还衍生出了一个价值数十亿美元的产业，专门说服大家掏钱把脂肪减掉。
But fat isn't an enemy.
问题是，脂肪并不是我们的敌人。
We spend so much time and money trying to eliminate it that we never give fat a proper chance to amaze us.
我们投入了大量的金钱和时间消灭脂肪，却没有给脂肪一个自我辩白，给它一个惊艳我们的机会。
Our fat is an evolutionary advantage, allowing us to store a lot of energy and relatively dense packages.
脂肪是有进化优势的，它能帮助我们储存大量的能量，拥有一个相对紧实的躯体。
Like we talked about in the last episode, gram for gram, that is the most efficient way to store energy in our bodies.
就像我们在上期视频中谈到的那样，一克一克地储存，这才是我们的身体储存能量最有效的方式。
And it's not just a storage center.
而且，脂肪不仅是一个储存中心。
It's an ever-changing organ that contributes to our well-being.
它还是一个一直处于变化之中且有助于我们机体健康的器官。
In today's episode, we'll learn about what our fat does and hopefully walk away a little more excited that it exists.
在今天的这期节目中，我们就来了解一下脂肪的具体功能，希望大家看完本期视频，对脂肪的感受能好一点。
As a quick disclaimer, we're not talking about dietary fats, like the one from oil, butter, or meats.
一个简短的免责声明，我们今天要谈论的不是膳食脂肪，就是食用油、黄油或肉类产生的脂肪。
This video focuses on fat as adipose tissue.
我们要谈论的是作为脂肪组织的脂肪。
A collection of different cells that we have in different locations in our bodies.
也就是我们身体不同位置的不同脂肪细胞组成的整体。
This type of tissue is made of endothelial cells, a few immune cells, but mostly, a special type of cell called adipocytes.
构成这种类型的组织的细胞有内皮细胞，部分免疫细胞，但主要是由一种特殊类型的，名为“脂肪细胞”的细胞。
In every gram of adipose tissue, you'll find anywhere from one to two million adipocytes.
每克脂肪组织脂肪细胞的个数少则一百万，多则两百万。
Here's what I think is so cool.
而我觉得脂肪细胞超酷的原因在于
That cells aren't passive structures.
这些细胞并不是被动的存在。
Adipocyte has cyte in the name.
脂肪细胞的名字里有“细胞”两个字。
So we know that it's a living, metabolizing cell.
所以我们知道，它是一个活生生的，会新陈代谢的细胞。
And if we zoom in on it, we can see cell structures like a nucleus with DNA in it.
如果我们把它放大，我们可以看到它的细胞结构里是有细胞核，有DNA的。
But most of its body is a storage site for lipid.
但绝大部分还是用来储存脂肪了。
The energy storage we're so interested in.
也就是我们非常感兴趣的储存能量的地方。
We have about 30 billion fat cells.
我们体内有大约300亿个脂肪细胞。
And when we store some excess energy, the cells will grow in size,
当我们储存了多余的能量时，脂肪细胞就会变大，
then if they can't grow anymore but you still need to store energy,
但如果它们已经大到不能再大了，而你还需要储存能量的话，
you'll grow new fat cells so you can store more energy.
你就会长出新的脂肪细胞，这样你就可以储存更多的能量了。
Now, when we see pictures of body fat, it's usually shown as a lumpy yellow tissue.
我们看到身体脂肪的图片时，图片你通常都是一块黄色的组织。
And it's true.
没错。
That is a type of fat that exists.
有一种脂肪确实是这样子的。
But that's not the only type of fat we have.
但这种脂肪并不是我们拥有的唯一一种脂肪。
The type of fat you're used to seeing is probably visceral fat.
大家经常看到的那种脂肪很可能是内脏脂肪。
Visceral just means that it's in the abdomen, surrounding your internal organs.
内脏的意思是说它是长在你腹部，将你的内脏包围起来了的脂肪。
This is what's often called belly fats, although there's a little more to it than that.
这也就是人们经常所说的“腰上的脂肪”，尽管它其实并不止长在腰部这个位置。
We have another layer of fat underneath our skin called subcutaneous fat.
我们的皮肤下面还有一层脂肪，这种脂肪叫“皮下脂肪”。
Sub for under, cutaneous for skin.
“Sub”就是下面的意思，cutaneous则是皮肤的意思。
If you have skin, this stuff is under it.
如果你有皮肤，那你的皮肤下面就有这种东西。
That means the skin under butt, chest, thighs, and yep, the abdomen.
这就意味着臀部、胸部、大腿，是的，还有腹部的皮肤下层都有这种脂肪。
Subcutaneous fat is used mostly for energy storage and some, but not a ton, of insulation.
皮下脂肪主要的功能是储存能量，还有隔热，但后一种作用并不是很大。
We keep fat in a few other sneaky spots too.
除了上面那些地方，其他比较不显眼的地方也会长脂肪。
Some fat has more of a mechanical purpose, like the fat that supports the eyes, and the fat pads that cushion the heels.
有些脂肪主要发挥的是力学作用，比如支撑眼睛的脂肪，缓冲脚后跟的脂肪垫等。
And we have that between some of our skeletal muscle fibers.
某些骨骼肌纤维之间也有这种脂肪。
It doesn't matter if you have a lot of body fat, or if you're very lean, everyone has fat in their muscles.
此外，无论你的体型是脂肪比较多的体型，还是比较纤瘦的体型，你的肌肉里都含有脂肪。
Fun fact, you can see intramuscular fat as the marbled in a cut of steak.
有趣的是，你可以直接在带大理石纹的牛排里看到肌肉脂肪。
Along with the visceral and subcutaneous fat, these locations of fat make up your white adipose tissue.
这些位置的脂肪和内脏脂肪，皮下脂肪都属于白色脂肪组织。
That adipocyte we showed you earlier was an example of white adipose tissue.
前面给大家展示的这种脂肪细胞就是白色脂肪组织的一个例子。
But you also have a separate type called brown adipose tissue,
但大家的体内还有另外一种脂肪组织——棕色脂肪组织，
which mostly exists so we can create body heat.
这种脂肪组织的主要作用是制造体热。
Its cell looks a little different.
这种脂肪组织的细胞长的和前面那种不太一样。
Check out how it has multiple lipid droplets compared to white adipocytes.
和白色脂肪组织细胞相比，这种脂肪组织细胞的脂滴更多。
But it's also got quite a few more mitochondria.
不仅如此，这种细胞的线粒体也更多。
And it's surrounded by blood vessels and nerves so it can heat up the blood.
而且，它的周围都是血管和神经，因为这样它才能让血液升温啊。
Brown fat is especially useful when you're a baby.
棕色脂肪对婴儿作用比较大。
Newborns can't shiver for warmth.
因为新生儿还不能靠抖取暖。
So they rely on brown fat to stay toasty.
所以他们就需要依靠棕色脂肪组织来维持身体的温度。
Ha, babies are useless.
哈，婴儿就是垃圾。
As you get older though, you develop other strategies to stay warm, like shivering, or just putting on a hoodie.
不过，随着年龄的增长，你会逐渐掌握其他的保暖策略，比如抖啊，或者直接套个帽衫。
This brown adipose tissue was more useful for our ancestors who were exposed to the elements.
其实，相比我们，这种棕色脂肪组织对我们的祖先来说更有用，因为他们经常要暴露在自然环境之下。
Plus, this tissue is only found in mammals so other animals use it to help them keep warm too.
此外，目前，人们只在哺乳动物身上发现了这种组织，也就是说，其他动物也会利用这种组织来保暖。
Although there are some circumstances where we will use it as adults,
不过，作为现代人的我们，成年以后，我们有时也还是会用到这种组织，
like if we're knocked out during general anesthesia and our bodies detect low body temperature,
比如，我们在全麻过程中被麻昏了，我们的身体又检测到我们体温较低的时候，
you're definitely not putting on a hoodie then, on account of, you know, being knocked out and everything.
那时候你肯定没办法套帽衫了对吧，因为你已经被麻晕了嘛。
