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We have this idea that if we want to lose weight,
想减肥的时候，我们会觉得
we join a gym on January 1st, we start working out regularly,
新年一开始我们就报个健身俱乐部，开始规律地健身
and eventually we’ll slim down.
最后我们肯定能瘦下来
Well, here’s some bad news.
好吧，我得告诉你一个坏消息
I read more than sixty studies on this,
我看过60多个关于健身减肥的研究
And it turns out exercise is actually pretty useless when it comes to weight loss.
结果发现，锻炼对减肥其实并没有多大帮助
Dr. Kevin Hall at the National Institutes of Health
国家卫生研究院的Kevin Hall博士
has done some of the most important studies on exercise and weight loss
是运动减肥研究方面的标杆人物
We need to rebrand exercise … exercise isn’t a weight loss tool per se,
我们需要重新定义锻炼一词……从本质上讲，锻炼并不能帮助我们减肥
it's excellent for health
通过锻炼保持身体健康是再好不过了
It is probably the best single thing that you can do other than stopping smoking to improve your health.
运动可能是除戒烟以外促进身体健康最有效的办法了
But don’t look at it as a weight loss tool.
但是，请不要以为它可以帮我们减肥
Exercise will definitely help you live a longer, happier life….
锻炼身体的确能帮我们健康长寿，过得更开心
It’s just not the best way to lose weight.
但它也的确不是减肥的好办法
And the reason has to do with how our bodies use energy.
其中的原因跟我们身体消耗能量的方式有关
You may not realize it,
你可能还没有意识到
but physical activity is actually a tiny component of your daily energy burn.
但身体活动消耗的能量其实只占了我们日常能量消耗中很小的一部分
There are three main ways our bodies burn calories.
我们的身体消耗能量主要有三种方式
These include your resting metabolism,
其中包括静止期代谢
So that's how much energy your body burns just for its basic functioning,
也就是你的身体维持最基本的官能
just to keep you alive, basically.
大体就是维持生命所消耗的能量
The other part of energy expenditure is the thermic effect of food,
另一部分能量消耗跟食物的热效应有关
and that’s just how much energy is required to break food down in your body.
也就是食物在体内消化所耗的能量
The third part of energy expenditure is physical activity.
第三部分能量代谢则是身体活动
For most people, physical activity - that’s any movement you do,
大部分人进行的身体活动——包括任何肢体活动——
only accounts for about 10 to 30 percent of energy use.
只消耗了身体的10%到30%的能量
So the vast majority of energy or calories you burn every day
所以，你每天的能量代谢主要
comes from your basal or resting metabolism,
都来自于最基础的静止期代谢
over which you have very little control.
而我们对静置期代谢的控制非常有限
While 100% of your “calories in” are up to you,
虽然你摄入多少热量完全取决于你自己
only up to about 30% of your “calories out” are in your control.
但能量的代谢你却只有30%的控制权
One study found that if a 200-pound man ran for an hour,
有研究发现，一个体重200磅的男子每天跑步一小时
4 days a week for a month,
一周跑四天，一个月下来
he’d lose about 5 pounds at most,
他最多也只能减5磅左右
assuming everything else stays the same.
前提是其他条件保持不变
And everything else doesn’t stay the same!
但哪有什么东西会保持不变！
Researchers have found we make all kinds of behavioral and physiological adaptations
研究人员发现，一旦我们开始增加每天的运动量，
when we start increasing the amount of exercise we’re getting every day.
我们就会做出各种行为和心理调整
For one thing, exercise tends to make people hungry.
一方面，运动通常会增加人们的饥饿感
And I'm sure you know the feeling:
我想你一定有过这种感觉：
you go for a spinning class in the morning,
早上你去参加动感单车课程
and then by the time you eat breakfast, you're so hungry
到吃早饭的时间你就会感到饥饿无比
you maybe double the size of the portion of oatmeal you normally eat.
那你可能会吃比平时多出一倍的燕麦
There's also evidence to suggest that
还有证据显示
some people simply slow down after a work out,
锻炼之后有些人会放慢生活节奏
so if you went running in the morning
比如你晨跑过后
you might be less inclined to take the stairs at work.
去上班时可能就不大愿意爬楼梯了
These are called “compensatory behaviors” --
这种现象叫作“补偿行为”——
They are basically the various ways we unknowingly undermine our workouts.
大体就是我们不知不觉减少运动量的各种方式
Researchers have also discovered a phenomenon called metabolic compensation.
研究者还发现了另一个所谓“代谢补偿”的现象
As people start to slim down, their resting metabolism can slow down.
随着人们身形变得苗条，他们的静止期代谢也会减少
So the amount of energy you burn while at rest is lower.
也就是说，你在休息的时候消耗的能量会更少
That means this bar might shrink as you start to lose weight.
也就意味着这一部分能量代谢会随着你体重的下降而降低
There’s still a lot of research to be done,
尽管这方面的研究还任重道远
but one study from 2012 is particularly interesting.
但2012年有研究人员做了一个格外有趣的研究
They went out into the middle of the Savannah in Tanzania
他们去了坦桑尼亚的热带草原
to measure the energy burn among a group of hunter gathers called the Hadza.
去测量那里一群当地人称之为“Hadza”的猎人的能量消耗情况
These are super-active, lean hunter-gatherers.
这些猎人身体非常纤长，而且超级有活力
They’re not spending their days behind a computer at a desk.
他们可不是每天都对着电脑的人
And what they found was shocking.
结果令他们大吃一惊
What we found is that there was no difference at all.
我们发现，他们的能耗跟我们并没有什么区别
So even though the Hadza have a much more physically active lifestyle,
也就是说，尽管Hadza们在生活中所做的体力活动远比我们多
they weren't burning any more calories every day than adults in the US and Europe.
他们每天消耗的能量却并不比美国或是欧洲的成年人多
Somehow the energy they used for physical activity was being offset or conserved elsewhere.
不知为何，他们体力活动消耗的能量从其他地方得到了补偿
So how do they stay slim? They don’t overeat.
那他们是怎么保持身材的？控制饮食
We can undo the calories that we burn off in exercise pretty quickly.
健身消耗的能量，很快就能找补回来
It would take about an hour of running to burn off a Big Mac and fries.
一个巨无霸和一些油炸食品带来的热量需要跑一个小时的步才能抵消掉
You’d have to spend about an hour dancing pretty vigorously
充满活力地跳一个小时的舞
to burn off three glasses of wine you might drink with dinner.
才能消耗掉晚饭时喝的三杯酒
An hour of cycling really intensely on exercise bikes to burn off about two doughnuts.
在健身脚踏车上高强度锻炼一小时消耗的差不多是两个甜甜圈的热量
That’s why exercise is best seen as a healthy supplement for a strategy that’s focused on food.
这就是为什么我们认为，健身不过是以控制饮食为主的健身策略最健康的辅助运动
But despite extremely high obesity rates in the US,
然而，尽管美国的肥胖率极高
government agencies continue to present exercise as a solution...
政府部门仍旧将健身视为降低肥胖率的一个方案
as do companies with a real interest in making sure we keep eating and drinking their products.
正如那些表面支持大家健身，实则巴不得我们一直吃他们的食品的企业一样
Since the 1920s,
二十世纪二十年代以来
companies like Coca-Cola have been aligning themselves with the exercise message.
可口可乐等企业一直都把自己与运动理念相挂钩
The idea here is that you can drink all these extra bottles of soda as long as you work out.
他们传递的信息就是，只要你锻炼，就可以随心所欲地喝他们那些苏打饮料
But as we're seeing, it doesn't work like that.
但我们看到的并不是那么回事
Actually burning off those extra calories from a can of soda is really, really hard.
实际上，要消耗多喝的一听苏打饮料真的是非常非常困难
We have an obesity problem in this country,
我们国家正面临着肥胖的问题
and we shouldn't treat low physical activity and eating too many calories as equally responsible for it.
但我们不应该觉得，缺乏体育锻炼和摄入过多热量对此有同样的责任
Public health policymakers should really prioritize improving our food environment
公共卫生的决策者们应该把改善食品环境放在第一位
to help people make healthier choices about what they eat.
帮助人们选择更健康的食品
It's not impossible to lose weight through exercise,
靠锻炼减肥并不是不可能
it's just a lot harder.
只不过要艰难得多
And we need to recognize how that works.
而且我们需要明白其中的原理
If you do go to the gym, and you burn all these calories,
如果你确实会去健身房，燃烧那些卡路里
it takes you a long time to do so and you put in a great amount of effort,
那你需要花更多的时间，投入大量的精力
you can erase all of that in five minutes of eating a slice of pizza.
但你投入的一切，都能在吃一片披萨的五分钟时间里全部化为泡影
It's relative magnitude,
这虽然只是一个相对值，
it's actually quite surprising, and most people don't fully appreciate that.
但这些发现实际上是很出乎意料的，而大多数人并没有真正明白这个道理
