MyOOPS開放式課程
請加入會員以使用更多個人化功能
來自全球頂尖大學的開放式課程,現在由世界各國的數千名義工志工為您翻譯成中文。請免費享用!
課程來源:TED
     

 

Sandra Aamodt 談為何減肥通常無效

Sandra Aamodt: Why dieting doesn't usually work

 

Photo of three lions hunting on the Serengeti.

講者:Sandra Aamodt

2013年6月演講,2014年1月在TEDGlobal 2013上線

 

翻譯:洪曉慧

編輯:朱學恆

簡繁轉換:洪曉慧

後製:洪曉慧

字幕影片後制:謝旻均

 

影片請按此下載

MAC及手持裝置版本請按此下載

閱讀中文字幕純文字版本

 

關於這場演講

在美國,80%女孩從十歲開始減肥。在這場坦誠、直率的演講中,神經學家Sandra Aamodt藉由個人經歷闡述了重要的一課,說明大腦如何管理身體,並探索其背後的科學根據,解釋為何減肥不僅無效,甚至可能得不償失。她提供了一些建議,告訴我們如何擁有不對體重過份在意的生活。

 

關於Sandra Aamodt

Sandra Aamodt探索與日常生活有關的神經科學,檢視新研究及其對人類自我認知的影響。

 

為什麼要聽她演講

Sandra Aamodt是神經學家及科普作家,她將複雜的神經科學研究轉變成有趣的讀物,使人們更深入瞭解自己的思想和行為。她的著作《大腦開竅手冊》及《兒腦開竅手冊》(均與王聲宏合著),目的在於使神經科學普及化,兩本著作均翻譯成多種語言。Aamodt的科學著作亦出現在《紐約時報》、《華盛頓郵報》、《世界報》及《倫敦時報》。

 

2003至2008年,Aamodt擔任《自然神經科學期刊》主編,這是大腦研究領域頂尖的科學期刊。她以大量科學背景知識解釋新研究,屏除神經科學謬論。職業生涯中,她審閱過5000篇以上的神經科學論文,並撰寫了許多科學政策方面的社論。

 

「如果人腦附帶使用說明書,或許就像這本書。」

-Dan Gilbert評論《大腦開竅手冊》

 

Sandra Aamodt的英語網上資料

Website: Sandra Aamodt

Twitter: @sandra_aamodt

Book: Welcome to Your Brain

Book: Welcome to Your Child's Brain

 

[TED科技‧娛樂‧設計]

已有中譯字幕的TED影片目錄(繁體)(簡體)。請注意繁簡目錄是不一樣的。

 

Sandra Aamodt 談為何減肥通常無效

 

三年半前,我做了此生最棒的決定之一,這是我的新年新希望。我放棄減肥,不再擔心體重,學習有意識地進食。現在我餓了就吃,我已瘦了10磅(約4.5公斤)。

 

這是十三歲的我,第一次嘗試減肥。現在看著這張照片,我心想,你需要的不是減肥,而是時尚顧問。(笑聲)但當時我自認需要減肥。當體重回升後,當然,我相當自責。之後三十年當中,我不斷嘗試各種減肥方法。無論我怎麼努力,減掉的體重總是再次回到我身上。我確信很多人都瞭解這種感覺。

 

身為神經科學家我想知道,為何減肥如此困難?顯然體重取決於攝取及消耗的熱量。大多數人不瞭解的是,飢餓感及能量消耗由大腦控制,多半與意識無關。大腦進行許多幕後工作。這是好事,因為你的意識-怎麼說比較禮貌?很容易分心。沉迷於電影中時,你不必記著呼吸這件事,這是好事。考慮晚餐吃什麼時,你不會忘了怎麼走路。

 

大腦對體重也有自己的想法,無論你的意識有何想法,這被稱為你的「設定值」。但這是誤導性名稱,因為事實上這個範圍大約是10至15磅(約4.5至7公斤)。你可藉由生活方式的選擇,使體重在這個範圍內升降,但超出這個範圍則難上加難。下視丘,大腦調節體重的部份。大腦中有十幾種導致體重增加的化學訊號,也有十幾種導致體重減輕的化學訊號。這個系統的運作方式就像恒溫器,對來自身體的訊號作出反應。藉由調整飢餓感、活動量及新陳代謝,因應環境的變化,維持體重的穩定。這就是恒溫器的運作方式,對嗎?它使室內溫度保持恆定,無論戶外的天氣如何變化。好,冬天時你可藉由打開窗戶改變室內溫度,但不會改變恒溫器的設定。它以啟動暖爐的方式做出回應,恢復室內溫度。大腦運作的方式完全相同。藉由強大的工具因應體重減輕,使體重回歸它認定的正常值。如果你的體重大幅減輕,大腦會認為你處於飢餓狀態,無論你最初是胖是瘦,大腦的反應完全相同。我們傾向於認為大腦能分辨你是否需要減肥,但並非如此。如果你的體重大幅減輕,你會感到飢餓,肌肉消耗的熱量隨之下降。哥倫比亞大學的Rudy Leibel博士發現,體重減輕10%的人,燃燒的熱量少了250至400卡路里,因為他們的新陳代謝受到抑制,那相當於一頓大餐。這意味著,成功的減肥者必須一輩子每天少吃這麼多熱量,相較於不須減肥而擁有相同體重的人。

 

從進化觀點來看,身體抗拒體重減輕是合理的,當食物短缺時。我們祖先的生存取決於能量的保存,在可獲得食物時恢復體重,以便抵禦下一次食物短缺。縱觀人類歷史,飢餓一向是比過度進食更嚴重的問題。這或許能解釋一個不幸的事實:體重設定值可能上升,但很難下降。如果你的母親曾說人生不公平,這正是她所說的那種情形。(笑聲)減肥成功不會降低你的設定值,即使你保持減肥成果長達七年,大腦依然試著恢復你的體重。如果體重減輕歸因於長期饑餓,這算是合理的反應。在速食氾濫的現代社會,這對許多人來說就不太適用了。古老過去和富足現代之間的差異,正是渥太華大學Yoni Freedhoff博士希望將一些病人送回食物匱乏時代的原因(如果時光機存在,將是世上最棒的減肥計劃)。這也是為何改變飲食環境是解決肥胖問題最有效的方法。

 

遺憾的是,一時的增重或許會成為永恆。如果超重狀態持續太久,對大多數人來說也許數年,大腦或許會認定那是新的正常值。

 

心理學家將進食者分為兩類:一種是視飢餓程度進食,一種是試著藉由意志力控制進食,如同大部份減肥者。好,我們姑且稱之為直覺型進食者及控制型進食者。令人感興趣的是,直覺型進食者比較不容易超重,他們較少思考食物的事。控制型進食者較容易受影響而過度進食,例如廣告、超大分量、吃到飽自助餐。小小的放縱,例如吃一匙冰淇淋,較容易引起控制型進食者暴飲暴食。孩童特別容易陷入減肥及暴食的循環。一些長期研究顯示,青春期早期曾經減肥的女孩,五年後超重的機率增加三倍,即使她們最初體重正常。所有研究均顯示,預測體重增加的同樣因素,亦可預測飲食障礙的發展。另一項因素,順帶一提,為人父母者請注意:被家庭成員嘲笑體重。所以千萬別這麼做。(笑聲)

 

我幾乎把所有圖表都留在家裡,但我忍不住帶來這張圖,因為我是個科技人,這樣才符合我的風格。(笑聲)這是一項觀察死亡風險的研究,持續進行了14年,藉由四種健康習慣:攝入足夠蔬果、每週運動三次、不吸菸、適度飲酒。我們先看研究中體重正常的群組。柱狀圖高度代表死亡風險,水平軸的0、1、2、3、4代表研究對象的健康習慣總數。如你所預期的,生活方式越健康,研究對象的死亡率越低。好,我們來看超重者的情形。沒有任何健康習慣的人死亡風險較高,僅僅多了一個健康習慣,即可把超重者拉回正常範圍。對沒有任何健康習慣的肥胖者來說,死亡風險相當高,比研究中最健康的群組高了七倍。但健康生活方式對肥胖者也有幫助。事實上,如果僅觀察擁有四種健康習慣的群組,你可以看見體重造成的差異十分微小。你可藉由控制生活方式來控制健康,即使你無法減重並繼續保持。

 

減肥並不是很可靠。減肥後五年內,大多數人的體重恢復原狀,其中40%甚至變得更胖。如果你思考這一點,典型的減肥結果,長期看來,增加的體重很可能比減掉的還多。

 

如果我已說服你們,減肥或許會造成問題。下一個問題是,該如何是好?我的回答,簡單地說,就是mindfulness(有意識地,亦有內觀之意)。我不是指你得學習冥想或上瑜珈課,我是指有意識地進食:學習瞭解身體的訊號。因此餓了就吃,飽了就停,因為體重增加多半歸因於不餓時進食。該怎麼做?允許自己盡情吃東西,然後試著瞭解身體在什麼情況下感到舒適。好好坐下,專心吃正餐,思考身體的感覺。當你開始進食及停止進食時,讓飢餓感決定何時該停止。我大約花了一年時間學習這一點,但相當值得。我這輩子不曾如此自在地與食物共處。我通常不會想到食物的事,我甚至忘了家裡有巧克力,彷彿被外星人洗腦,徹底改頭換面。我得告訴各位,這種飲食方法或許不會減輕你的體重,除非你經常在不餓的狀態下進食。但對許多人來說,醫生無法提供任何明確的減重方式,這就是為何目前許多人關心的是如何預防體重增加,而不是提倡減肥。面對現實吧:如果減肥有用,我們早就瘦下來了。(笑聲)為何我們一再做相同的事,卻期待不同結果?減肥或許看似無害,但確實引起許多副作用,最壞的情況是損害健康:太過在意體重會導致飲食障礙,特別是青少年。在美國,80%十歲女童承認自己曾經減肥,我們的女兒以錯誤的標準衡量自我價值。即使在最好的情況下,減肥也得耗費時間和精力。它耗費了你可使用的意志力,例如輔導孩子做功課,或完成重要的工作計畫。因為意志力是有限的,任何減肥策略都將持續消耗意志力。這幾乎注定了最終失敗的結果,當你的注意力轉移到其他地方時。

 

最後我再分享一個想法。如果我們告訴所有減肥的女孩:「餓了就吃沒關係。」會如何?如果我們教導她們與食慾和平共處,而非懼怕它?我認為大部份女孩會更快樂、更健康。當她們成年後,或許很多人都會變瘦。我希望十三歲時有人告訴我這些。

 

謝謝。

 

(掌聲)

 

以下為系統擷取之英文原文

About this talk

In the US, 80% of girls have been on a diet by the time they're 10 years old. In this honest, raw talk, neuroscientist Sandra Aamodt uses her personal story to frame an important lesson about how our brains manage our bodies, as she explores the science behind why dieting not only doesn't work, but is likely to do more harm than good. She suggests ideas for how to live a less diet-obsessed life, intuitively.
 
About Sandra Aamodt
Sandra Aamodt explores the neuroscience of everyday life, examining new research and its impact on our understanding of ourselves.
 
About the transcript
Three and a half years ago, I made one of the best decisions of my life. As my New Year's resolution, I gave up dieting, stopped worrying about my weight, and learned to eat mindfully. Now I eat whenever I'm hungry, and I've lost 10 pounds.
 
This was me at age 13, when I started my first diet. I look at that picture now, and I think, you did not need a diet, you needed a fashion consult. (Laughter) But I thought I needed to lose weight, and when I gained it back, of course I blamed myself. And for the next three decades, I was on and off various diets. No matter what I tried, the weight I'd lost always came back. I'm sure many of you know the feeling.
 
As a neuroscientist, I wondered, why is this so hard? Obviously, how much you weigh depends on how much you eat and how much energy you burn. What most people don't realize is that hunger and energy use are controlled by the brain, mostly without your awareness. Your brain does a lot of its work behind the scenes, and that is a good thing, because your conscious mind -- how do we put this politely? -- it's easily distracted. It's good that you don't have to remember to breathe when you get caught up in a movie. You don't forget how to walk because you're thinking about what to have for dinner.
 
Your brain also has its own sense of what you should weigh, no matter what you consciously believe. This is called your set point, but that's a misleading term, because it's actually a range of about 10 or 15 pounds. You can use lifestyle choices to move your weight up and down within that range, but it's much, much harder to stay outside of it. The hypothalamus, the part of the brain that regulates body weight, there are more than a dozen chemical signals in the brain that tell your body to gain weight, more than another dozen that tell your body to lose it, and the system works like a thermostat, responding to signals from the body by adjusting hunger, activity and metabolism, to keep your weight stable as conditions change. That's what a thermostat does, right? It keeps the temperature in your house the same as the weather changes outside. Now you can try to change the temperature in your house by opening a window in the winter, but that's not going to change the setting on the thermostat, which will respond by kicking on the furnace to warm the place back up. Your brain works exactly the same way, responding to weight loss by using powerful tools to push your body back to what it considers normal. If you lose a lot of weight, your brain reacts as if you were starving, and whether you started out fat or thin, your brain's response is exactly the same. We would love to think that your brain could tell whether you need to lose weight or not, but it can't. If you do lose a lot of weight, you become hungry, and your muscles burn less energy. Dr. Rudy Leibel of Columbia University has found that people who have lost 10 percent of their body weight burn 250 to 400 calories less because their metabolism is suppressed. That's a lot of food. This means that a successful dieter must eat this much less forever than someone of the same weight who has always been thin.
 
From an evolutionary perspective, your body's resistance to weight loss makes sense. When food was scarce, our ancestors' survival depended on conserving energy, and regaining the weight when food was available would have protected them against the next shortage. Over the course of human history, starvation has been a much bigger problem than overeating. This may explain a very sad fact: Set points can go up, but they rarely go down. Now, if your mother ever mentioned that life is not fair, this is the kind of thing she was talking about. (Laughter) Successful dieting doesn't lower your set point. Even after you've kept the weight off for as long as seven years, your brain keeps trying to make you gain it back. If that weight loss had been due to a long famine, that would be a sensible response. In our modern world of drive-thru burgers, it's not working out so well for many of us. That difference between our ancestral past and our abundant present is the reason that Dr. Yoni Freedhoff of the University of Ottawa would like to take some of his patients back to a time when food was less available, and it's also the reason that changing the food environment is really going to be the most effective solution to obesity.
 
Sadly, a temporary weight gain can become permanent. If you stay at a high weight for too long, probably a matter of years for most of us, your brain may decide that that's the new normal.
 
Psychologists classify eaters into two groups, those who rely on their hunger and those who try to control their eating through willpower, like most dieters. Let's call them intuitive eaters and controlled eaters. The interesting thing is that intuitive eaters are less likely to be overweight, and they spend less time thinking about food. Controlled eaters are more vulnerable to overeating in response to advertising, super-sizing, and the all-you-can-eat buffet. And a small indulgence, like eating one scoop of ice cream, is more likely to lead to a food binge in controlled eaters. Children are especially vulnerable to this cycle of dieting and then binging. Several long-term studies have shown that girls who diet in their early teenage years are three times more likely to become overweight five years later, even if they started at a normal weight, and all of these studies found that the same factors that predicted weight gain also predicted the development of eating disorders. The other factor, by the way, those of you who are parents, was being teased by family members about their weight. So don't do that. (Laughter)
 
I left almost all my graphs at home, but I couldn't resist throwing in just this one, because I'm a geek, and that's how I roll. (Laughter) This is a study that looked at the risk of death over a 14-year period based on four healthy habits: eating enough fruits and vegetables, exercise three times a week, not smoking, and drinking in moderation. Let's start by looking at the normal weight people in the study. The height of the bars is the risk of death, and those zero, one, two, three, four numbers on the horizontal axis are the number of those healthy habits that a given person had. And as you'd expect, the healthier the lifestyle, the less likely people were to die during the study. Now let's look at what happens in overweight people. The ones that had no healthy habits had a higher risk of death. Adding just one healthy habit pulls overweight people back into the normal range. For obese people with no healthy habits, the risk is very high, seven times higher than the healthiest groups in the study. But a healthy lifestyle helps obese people too. In fact, if you look only at the group with all four healthy habits, you can see that weight makes very little difference. You can take control of your health by taking control of your lifestyle, even If you can't lose weight and keep it off.
 
Diets don't have very much reliability. Five years after a diet, most people have regained the weight. Forty percent of them have gained even more. If you think about this, the typical outcome of dieting is that you're more likely to gain weight in the long run than to lose it.
 
If I've convinced you that dieting might be a problem, the next question is, what do you do about it? And my answer, in a word, is mindfulness. I'm not saying you need to learn to meditate or take up yoga. I'm talking about mindful eating: learning to understand your body's signals so that you eat when you're hungry and stop when you're full, because a lot of weight gain boils down to eating when you're not hungry. How do you do it? Give yourself permission to eat as much as you want, and then work on figuring out what makes your body feel good. Sit down to regular meals without distractions. Think about how your body feels when you start to eat and when you stop, and let your hunger decide when you should be done. It took about a year for me to learn this, but it's really been worth it. I am so much more relaxed around food than I have ever been in my life. I often don't think about it. I forget we have chocolate in the house. It's like aliens have taken over my brain. It's just completely different. I should say that this approach to eating probably won't make you lose weight unless you often eat when you're not hungry, but doctors don't know of any approach that makes significant weight loss in a lot of people, and that is why a lot of people are now focusing on preventing weight gain instead of promoting weight loss. Let's face it: If diets worked, we'd all be thin already. (Laughter) Why do we keep doing the same thing and expecting different results? Diets may seem harmless, but they actually do a lot of collateral damage. At worst, they ruin lives: Weight obsession leads to eating disorders, especially in young kids. In the U.S., we have 80 percent of 10-year-old girls say they've been on a diet. Our daughters have learned to measure their worth by the wrong scale. Even at its best, dieting is a waste of time and energy. It takes willpower which you could be using to help your kids with their homework or to finish that important work project, and because willpower is limited, any strategy that relies on its consistent application is pretty much guaranteed to eventually fail you when your attention moves on to something else.
 
Let me leave you with one last thought. What if we told all those dieting girls that it's okay to eat when they're hungry? What if we taught them to work with their appetite instead of fearing it? I think most of them would be happier and healthier, and as adults, many of them would probably be thinner. I wish someone had told me that back when I was 13.
 
Thanks.
 
(Applause)

留下您對本課程的評論
標題:
您目前為非會員,留言名稱將顯示「匿名非會員」
只能進行20字留言

留言內容:

驗證碼請輸入9 + 7 =

標籤

現有標籤:1
新增標籤:


有關本課程的討論

目前暫無評論,快來留言吧!

Creative Commons授權條款 本站一切著作係採用 Creative Commons 授權條款授權。
協助推廣單位: