第27讲 吃还是不吃？—饮食的生理与心理在线视频

今天我们要讲的内容是饮食动机
What we are going to talk about today is dietary motivation

一说饮食
When it comes to diet

我就觉得饿了
I feel hungry

我们为什么会饿
Why are we hungry?

饿了就一定会吃东西吗
Will you eat when you are hungry?

吃什么
What to eat?

吃多少
How much to eat?

什么时候吃
When do you want it?

其实
In fact

所有问题都值得研究
all the problems are worth studying

第一个问题
First

我们为什么会饿呢
why are we hungry?

很多人认为
Many people think that

我们的胃里没东西了
if we have nothing in our stomach

就会感到饥饿
we will feel hungry

是不是这样呢
Is that so?

著名生理心理学家坎农在一项实验中
In an experiment, Cannon, a famous physiological psychologist

让他的一个研究生吞下一个
asked a graduate student to swallow

没有充气的气球然后往气球里面打气
an inflated balloon and pump air into it

当这个学生的胃收缩时
When the student's stomach contracted

空气就排出来
the air was discharged

这样可以精确记录排出气体的量
which made it possible to accurately record the amount of air discharged

结果发现
The results showed that

当胃收缩的时候
when the stomach contracted

学生就感受到饥饿
the student felt hungry

这似乎说明
This seems to indicate that

饥饿是由胃部收缩所引起的
hunger is caused by contraction of the stomach

但后来的研究发现
But later studies found that

用外科手术把胃切除以后
after surgical gastrectomy

病人仍然能体验到饥饿
patients still experienced hunger

所以
Therefore

空胃不是产生饥饿的必要条件
empty stomach is not a necessary condition for hunger

那么胃里塞满食物能阻止进食吗
Can filling your stomach with food stop you from eating?

我们的身体对胃部压力的来源很敏感
The body is very sensitive to the source of gastric pressure

所以 当食物填满胃部
so when food fills the stomach

即使我们吃的是最喜欢的东西
even if what we eat is our favorite food

也没胃口了
we have no appetite

这种现象叫感觉特异性饱食感
This phenomenon is called sensory-specific satiety

能让我们迅速消除吃东西的欲望
which can quickly eliminate our desire to eat

但是
However

这种饱食感针对的是特定的味道
this satiety is related to a specific taste

而不是食物本身
not the food itself

也就是说
That is to say

如果我们吃某种食物吃饱了
if we are full of a certain food

但当食物味道发生了改变
but when the taste of the food changes

我们就重新对食物感兴趣
we will be interested in the food again

所以如果一顿饭的食物类型很多
So if there are many types of food in a meal

你的胃口就会更好
your appetite will be better

20世纪50年代以来
Since the 1950s

生理学家发现动物的外侧下丘脑
physiologists have found that the lateral hypothalamus

是进食中枢
is the feeding center

腹内侧下丘脑是饱足中枢
and the ventromedial hypothalamus is the satiety center

刺激进食中枢
If the feeding center is stimulated

动物就进食更多自己喜欢的食物
the animal will eat more of its own favorite food

刺激饱足中枢
If the satiety center is stimulated

动物就停止进食
the animal will stop eating

当血液中的糖和脂肪浓度发生变化
When the concentration of sugar and fat in the blood changes

信息就被传到进食中枢和饱足中枢
the information is transmitted to the feeding center and the satiety center

动物就会进食或停止进食
and the animal will eat or stop eating

如果我们的进食中枢受到刺激
If our eating center is stimulated

我们感受到了饥饿
and we feel hungry

就一定会吃东西吗
will we eat?

实际上
In fact

我们吃不吃东西
whether we eat or not

吃什么东西
and what to eat

受文化规范和习俗的影响
is influenced by cultural norms and customs

现在我们谈论饮食
Now when we talk about diet

很多时候都与保持体形有关
it's often about keeping fit

很多人都害怕自己变胖了
Many people are afraid of getting fat

那么胖 瘦有什么标准吗
So what's the standard size for figure?

研究者使用身体质量指数（BMI）
The researchers used body mass index (BMI)

来确定是否超重和肥胖
to judge whether they were overweight or obese

计算方法是把以公斤为单位的重量
The calculation is to divide the weight in kilograms

除以以米为单位的身高的平方
by the square of the height in meters

BMI在25-29.9之间为超重
BMI between 25-29.9 means overweight

BMI超过30就是肥胖
BMI more than 30 means obesity

比如
For example

我体重85公斤
I weigh 85 kilograms

身高1.86米
and am 1.86 meters tall

BMI就是85除以1.86的平方
My BMI is 85 divided by 1.86 square meters

大概是24.6
It's about 24.6

还没有达到25这个超重的标准
I haven't reached the overweight standard of 25 yet

不过也快了
but almost

为什么有的人会超重
Why are some people overweight?

我们可以设想一下
Let's imagine the scene

我们的祖先多数时候是否有足够的食物呢
if our ancestors had enough food most of the time?

恐怕多数时候都没有足够的食物
I don't think they have enough food most of the time

所以 一旦他们有机会得到很多食物
so once they had a chance to get a lot of food

就会大吃特吃
they would eat a lot

有的人吃多了就长胖了
Some people got fat after they ate too much

有的人却没有长胖
while others didn't

那些长胖的人生存下去的概率就会更高
Those who got fat were more likely to survive

当食物缺乏的季节来临时
When the season of food shortage came

长胖的人就会消化体内的脂肪
the fat people would consume the fat

来应对饥饿
in their bodies to deal with hunger

有的人只用了很短的时间
Some people consumed the fat

就消耗了脂肪
only in a short time

有的人则用了几个月
Some people consumed the fat

才把体内的脂肪消耗完
in their bodies in a few months

那些能撑的时间较长的人
Those who could last for a long time

就更容易生存下去
were more likely to survive

所以
As a result

自然选择使我们人类形成了一种倾向
natural selection has made us form a tendency

一吃东西就容易长胖
to grow fat as soon as we eat a lot

但吃很少东西却不容易变瘦
but not easy to become thin when we eat very little

这样
In this way

我们就好理解后面所提到的
we can understand the influencing factors of

关于肥胖的影响因素了
obesity mentioned later

科学家认为
Scientists have found that

遗传因素对肥胖有重要影响
genetic factors play an important role in obesity

有些人喝凉水也会长肉
Some people "grow meat even drink water only"

他们真的是吃得很少也会长胖
they really grow fat even they eat little

这其实是进化的倾向
This is actually the tendency of evolution

通过遗传在起作用
to work through gene

营养因素也很重要
Nutrition is also important

我们现在的食物太丰富了
Our food is too rich

味道太好了营养太充足了
delicious and nutritious

我们很难忍受美食的诱惑
We can't stand the temptation of delicious food

所以就吃了很多东西就胖了
so we're fat after eating a lot

这其实是进化所形成的
This is actually a protection mechanism formed in

一种保护机制
the process of evolution

另外有心理学家发现
Other psychologists have found that

人们对食物和饮食行为的思维方式有差异
people have different ways of thinking about food and eating behavior

有的人属于不限制性饮食者
Some people are unrestrained eaters

他们不考虑节食问题
They don't think about dieting

他们不担心自己吃的太多
and don't worry about eating too much

另外一种是限制性饮食者
Others are restrained eaters

他们总是对食物量加以限制
They always limit the amount of food

对食物感到焦虑
and feel anxious about it

但他们一旦放弃限制
But once they give up the restraint

就会暴饮暴食
they will overeat

而生活中很多因素
and many factors in life will

都会导致他们放弃限制
lead them to give up the restraint

比如 当他们对自己的能力感到失望
For example, when they feel disappointed

或者感到尊严受到伤害
in their abilities or their dignity is hurt

就很容易取消对食物的限制
it's easy to remove the restraint on food

就会很快长胖
and gain weight quickly

任何推动我们吃东西的心理活动
Any mental activity that drives us to eat

其实都是保护我们
is actually an evolutionary mechanism

免受饥饿的进化机制在起作用
that works to protect us from hunger

所以肥胖是很容易的
So it's easy to be fat

但从长远来说
but in the long run

减肥却极其困难
it's extremely difficult to lose weight

限制饮食会带来怎样的后果呢
What are the consequences of dietary restraints?

很多人因为过分限制饮食出现了饮食障碍
Many people suffer from eating disorders due to over restraint of diet

有三种饮食障碍
There are three eating disorders

第一种是神经性厌食症
The first is anorexia nervosa

如果一个人的体重比他期望体重的85%
If a person's weight is lower than 85%

还要低
of his expected weight

就可以诊断为神经性厌食症
the person can be diagnosed as anorexia nervosa

这种病人拒绝吃太多东西
These patients refuse to eat too much

体重已经严重下降
have lost a lot of weight

仍然担心变胖
and are still worried about getting fat

比如法国模特伊莎贝尔·卡罗
French model Isabelle Caro, for example

就因为过度饮食
suffered from anorexia nervosa

得了神经性厌食症
because she was on an excessive diet

很多神经性厌食症患者
Many anorexia nervosa patients also suffer from

同时还患有第二种饮食障碍
the second type of eating disorder

就是神经性贪食症
bulimia nervosa

他们毫无节制地狂吃
They overeat without restraint

接着通过呕吐 泻药 绝食等方式消除体内的热量
and then eliminate the calories by vomiting, cathartic, fasting and other ways

两种饮食障碍都会造成营养不良
Both eating disorders can cause malnutrition

所以会影响生理机制
and affect physiological mechanisms

甚至能因为饥饿而死亡
and some persons even die of hunger

另外还有一种病人
In addition, there is a kind of patients

他们毫无节制的狂吃
who eat without restraint

但不像神经性贪食症那样
but do not take measures to eliminate excessive calories

采取措施消除体内过多的热量
in the body like bulimia nervosa

这就是第三种饮食障碍
This is the third kind of eating disorder

叫暴食症
called binge eating disorder

他们在疯狂进食的过程中
When they are eating crazily

会觉得自己失去了理智
they will feel that they have lost their sense of reason

因而自己感觉非常痛苦
so they feel very painful

饮食障碍者以女性居多
Most people with eating disorders are women

但现在性别差异在逐渐缩小
but now the gender gap is narrowing

过去的男女比例约为1比10
In the past, the ratio of men to women was about one to ten

但在20世纪初
but at the beginning of the 20th century

已经变为1比3左右
it had become about one to three

美国大中学生每两百人中
There is one person with eating disorder

就有一个饮食障碍者
in every 200 American students

他们多数都是智慧较高
Most of them are good students with high intelligence

行为良好 做事认真 出身富家的好学生
good behavior, serious work and rich family background

科学家认为
Scientists believe that

饮食障碍与遗传因素有密切关系
eating disorders are closely related to genetic factors

而心理学家关注
Psychologists pay close attention to the

饮食障碍的心理因素
psychological factors of eating disorders

在我们的现代社会中
In our modern society

很多女性都在追求所谓 骨感美
many women are pursuing the so-called "backbone beauty"

媒体在不遗余力的宣传女性
The media is trying to promote the idea that

瘦即是美
"thin is beautiful"

这让人觉得
which makes people think that

只有苗条的女性才是漂亮的 有吸引力的
only slim women are beautiful and attractive

这让很多人
This makes a lot of people

尤其是成年女性
especially adult women

对自己的身材很不满
feel very dissatisfied with their bodies

为了追求苗条
In order to be slim

他们就过度节食
they go on excessive diet

这样就比较容易患饮食障碍
which is more likely to suffer from eating disorders

由于我们几乎不可能控制自己的体重
Since it's almost impossible for us to control our weight

所以我们不应该纠结自己的体重
we should not obsess about our weight

而应该把时间 精力和钱
but spend our time, energy and money

花在增强体质而不是减肥上面
on building up our body rather than losing weight

好 今天的内容就讲完了
OK, that's all for today

现在回顾一下主要内容
Now let's review the main content

科学家发现
Scientists have found that

感觉特异性饱食感
sensory-specific satiety

是调节进食的重要机制
is an important mechanism for regulating eating

下丘脑的进食中枢和饱足中枢
and the feeding center and satiety center of the hypothalamus

是调节进食的脑机制
are brain mechanisms for regulating eating

另外
In addition

体重主要受遗传因素
weight is mainly affected by genetic factors

营养因素和心理因素的影响
nutritional factors and psychological factors

减肥非常困难
It's very difficult to lose weight

但过分节食却可能会带来饮食障碍
but over dieting can lead to eating disorders

下次课我们会讨论什么样的人
Next lecture we will discuss what kind of people

更有可能努力追求成就
are more likely to strive for success

好 下次再见
OK, see you next time