Well, here’s some bad news.

但是我要告訴你一些壞消息。

I read more than sixty studies on this, and it turns out exercise is actually pretty useless when it comes to weight loss.

我讀了超過 60份的研究報告，發現運動實際上對減肥而言是沒有幫助的。

Dr. Kevin Hall at the National Institutes of Health has done some of the most important studies on exercise and weight loss.

美國國立衛生研究院的凱文·霍爾博士做了一些關於運動和減肥最重要的研究。

We need to rebrand exercise.

我們需要重新打造運動的形象

Exercise isn’t the weight loss tool per se. It's excellent for health.

運動本身並非一個減重工具，它對健康十分有益。

It's probably the best single thing that you can do other than stopping smoking to improve your health.

它大概是除了戒菸以外，你能改善健康的最佳活動了。

But don’t look at it as a weight loss tool. Exercise will definitely help you live a longer, happier life.

但是不要視它為減肥工具。運動一定可以幫你活得更長，活得更幸福

It’s just not the best way to lose weight.

它只是不是減肥的最佳途徑。

And the reason has to do with how our bodies use energy.

而理由和我們身體消耗能量的方式有關。

You may not realize it, but physical activity is actually a tiny component of your daily energy burn.

你可能沒有意識到，但體能活動實際上只是你每天能量燃燒中的一小部分。

There are three main ways our bodies burn calories.

我們身體燃燒熱量有三種主要的方式。

These include your resting metabolism, so that's how much energy your body burns just for its basic functioning, just to keep you alive, basically.

這些包含你的靜態代謝率，這指的是身體為了基礎運作而消耗的能量——基本上只是讓你活著的能量。

The other part of energy expenditure is the thermic effect of food, and that’s just how much energy is required to break food down in your body.

能量支出的另一個部分是食物熱效應，那是食物在你體內分解所需的能量。

The third part of energy expenditure is physical activity.

第三種的能量消耗就是體能活動。

For most people, physical activity - that’s any movement you do, only accounts for about 10 to 30 percent of energy use.

對多數人來說，體能活動——也就是你所做的任何動作，只佔大約百分之十到三十的整體能量消耗而已。

So the vast majority of energy or calories you burn every day comes from your basal or resting metabolism, over which you have very little control.

所以你每天絕大多數的能量或熱量消耗是來自你的基礎代謝或靜態代謝，而那些是你不太能掌控的。

While 100% of your "calories in" are up to you, only about 30% of your "calories out" are in your control.

你能百分之百的決定自己要攝取多少卡路里，但只有大概百分之三十的「熱量消耗」是由你控制的。

One study found that if a 200-pound man ran for an hour, 4 days a week for a month, he’d lose about 5 pounds at most, assuming everything else stays the same.

一項研究發現，如果一個兩百磅重的男人一個月下來每週跑步四天，每次跑一小時，他最多只能減掉大概五磅，而那是假設其他一切都不變的話。

And everything else doesn’t stay the same!

但其他一切並不會保持原狀！

Researchers have found we make all kinds of behavioral and physiological adaptations when we start increasing the amount of exercise we’re getting every day.

研究者發現我們會做出各種行為和生理上的調整，當我們開始增加每日運動量的時候。

For one thing, exercise tends to make people hungry.

一則是因為運動容易使人感到飢餓。

And I'm sure you know the feeling: you go for a spinning class in the morning,

我敢說你知道那種感覺：你早上去上一堂飛輪課，

and then by the time you eat breakfast you're so hungry you maybe double the size of the portion of oatmeal you'd normally eat.

然後到吃早餐的時候，你餓到可能會吃比平常多一倍的燕麥量。

There's also evidence to suggest that some people simply slow down after a workout.

還有證據顯示有些人在運動後會減緩步調。

So if you went running in the morning, you might be less inclined to take the stairs at work.

所以如果你那天早上去了跑步，你上班時可能就比較不傾向於爬樓梯。

These are called "compensatory behaviors".

這種行為被稱作「補償行為」。

They're basically the various ways we unknowingly undermine our workouts.

它們基本上是各種使我們不知不覺破壞運動效果的方式。

Researchers have also discovered a phenomenon called "metabolic compensation".

研究者還發現一種被稱作為「代謝補償」的現象。

As people start to slim down, their resting metabolism can slow down.

當人們開始瘦下來時，他們的靜態代謝率可能也會下降。

So the amount of energy you burn while at rest is lower.

所以你在休息時所消耗的能量也會比之前少。

That means that this bar might shrink as you start to lose weight.

這代表這個數據可能會在你開始減重時下降。

There’s still a lot of research to be done, but one study from 2012 is particularly interesting.

還需要更多的研究去證明，不過 2012 年的一項研究特別有意思。

They went out into the middle of the Savannah in Tanzania to measure the energy burn among a group of hunter-gatherers called the Hadza.

他們去到坦尚尼亞大草原的正中央，計算一群被稱作 Hadza 的採獵者的能量消耗。

These are super-active, lean hunter-gatherers.

這些是極為活躍、瘦削的採獵者。

They’re not spending their days behind a computer at a desk.

他們可不是整天坐在桌子前看電腦的人。

And what they found was shocking.

而他們發現的事情很令人震驚。

What we found is there was no difference at all.

我們發現他們的消耗能量完全沒有差異。

So even though the Hadza have a much more physically active lifestyle, they weren't burning any more calories every day than adults in the US and Europe.

所以儘管 Hadza 採獵者們過著較為活躍的生活，他們每天並沒有比住在美國和歐洲的成年人燃燒更多的卡路里。

Somehow the energy they used for physical activity was being offset or conserved elsewhere.

出於某種原因，他們用在身體活動的能量被抵銷或儲存在別的地方了。

So how do they stay slim? They don’t overeat.

那麼，他們是如何保持纖瘦的呢？他們不多吃。

We can undo the calories that we burn off in exercise pretty quickly.

我們可以很快就抵銷掉運動所燃燒的熱量。

It would take about an hour of running to burn off a Big Mac and fries.

我們需要跑上一小時的步才能燃燒一個漢堡包和薯條的熱量。

You’d have to spend about an hour dancing pretty vigorously to burn off three glasses of wine you might drink with dinner,

你得花大約一小時十分劇烈地舞動才能燃燒掉你可能在晚餐時喝的三杯酒；

an hour of cycling really intensely on exercise bikes to burn off about two doughnuts.

在健身腳踏車上賣力地踩一小時才能消耗掉大約兩個甜甜圈的熱量。

And that’s why exercise is best seen as a healthy supplement for a strategy that’s focused on food.

那就是為什麼運動最好被視為一種對身體有益、用來輔助以控制飲食為主要減重對策的手段。

But despite extremely high obesity rates in the US, government agencies continue to present exercise as a solution,

儘管美國有非常高的肥胖率，政府機關持續提倡運動為解決方法，

as do companies with a real interest in making sure we keep eating and drinking their products.

那些因為我們吃喝他們產品而獲利的公司也是這麼想的。

Since the 1920s, companies like Coca-Cola have been aligning themselves with the exercise message.

自 1920 年代起，一些公司像可口可樂就把自己和運動這訊息擺在一起。

The idea here is that you can drink all of these extra bottles of soda as long as you work out.

它的概念是，只要你運動，你就可以喝下這些所有超量的汽水。

But as we're seeing, it doesn't work like that.

但如我們所見，事情並不是那樣的。

Actually burning off those extra calories from a can of soda is really, really hard.

事實上，要消耗一罐汽水所產生的額外熱量是非常、非常的困難。

We have an obesity problem in this country, and we shouldn't treat low physical activity and eating too many calories as equally responsible for it.

我們的國家出現肥胖問題，我們不應該把過少運動和攝取太多熱量相題並論。

Public health policymakers should really prioritize improving our food environment to help people make healthier choices about what they eat.

衛生署決策者真的應該優先改善我們的食物環境，幫助人們在他們所吃的食物上做出更健康的選擇。

It's not impossible to lose weight through exercise, it's just a lot harder.

透過運動減重並非不可能，只是會困難很多。

And we need to recognize how that works.

而我們也必須知道那是怎麼的一回事。

If you do go to the gym, you burn all these calories, takes you a long time to do so and you put in a great amount of effort.

如果你真的去健身房燃燒掉所有熱量，這會花上你很長的時間，而且你要投入許多精力。

You can erase all of that in five minutes of eating a slice of pizza.

但你可以在五分鐘內吃下一塊比薩就讓那一切的努力化為烏有。

Relative magnitude is actually quite surprising, and most people don't fully appreciate that.

這相對的重要性其實頗為驚人，而且大多數人並不完全了解。