By Cen Rong Translation： Li Li

The Economist’s Weight-Loss Strategy

By Cen Rong Translation： Li Li

A study on people’s waistlines in the U.S. found that our f o o d i n t a k e h a s increased since the 1970s, while the energy we consume every day maintained at a steady level.Daily calorie intake increases by 300 kilojoules every decade.Obesity has now become a major problem that troubles people’s lives.

Economists found that bigger plates, bowls, and even pantries increase our food intake.

In a test, researchers put popcorn, which had been stored for 14 days in buckets of various sizes and then gave them to the audience at a cinema. It was found that the audience who took the bigger bucket ate 38%more expired popcorn than other people. It tells us that people decide to stop eating according to external information (i.e.my plate is empty) rather than internal information (I am full).

In another test, scientists randomly gave 10 weightloss strategies to participants and found two strategies most effective: participants who used smaller plates (dia<25cm) to eat lost an average of 0.9kg within one month; experimenters who were not allowed to watch TV while eating lost 0.7kg on average in one month.

Brian Wansink, director of the Cornell University Food and Brand Lab, found that people consumed 28%～55% more food while they watch sad movies;people eat less with softer lighting and soft jazz ballads playing; lower contrast between the color of the plate and color of the food makes people consume 22%～32% more food.

Apart from appetite control,keeping fit is another key to losing weight. Some economists tried to help people to keep exercising by providing incentives.In an experiment designed by Uri Gneezy, professor of economics from University of California, a group of students were separated into two groups: experimental group and control group. The experimental group was promised an additional$100 for attending the gym at least eight times over four weeks, while there was no incentive for the control group.

美國一項針對腰圍的研究發(fā)現：從1970年左右開始，我們身體每天的能耗就基本維持在一個穩(wěn)定的水平，但人們的食量開始增長，每過十年，我們的日均能量攝入量增長300千焦，于是肥胖成為一個困擾現代人的重大問題。

經濟學家們發(fā)現，更大的盤子、碗甚至是食品柜，都會增大我們的食量。

在一項實驗中，研究者把一些存放14天的爆米花，裝在不同規(guī)格的桶中分給電影觀眾，結果拿大桶爆米花的觀眾，比其他人多吃下38%的過期爆米花。這說明人們往往根據外部信息（我的盤子空了），而非內部信息（我飽了）停止進食。

在另一項實驗中，他們把10條減肥策略隨機分配給實驗參與者，最終他們發(fā)現最成功的兩條減肥策略：堅持用小盤子（直徑小于25厘米）進食的參與者，一個月內平均減掉0.9公斤；吃飯時禁止看電視的實驗者，一個月內平均減掉0.7公斤。

康奈爾大學食物與品牌實驗室主任布萊恩·萬辛克發(fā)現：看悲傷的電影會讓你多吃28%至55%的東西；餐廳中柔和的燈光和動聽的爵士樂會讓你吃得更少；所持餐盤的顏色與盤中食物的顏色色差較小，會讓人多吃22%至32%的食物。

除了控制食欲，減肥的另一個關鍵是健身。經濟學家試圖通過激勵機制讓人們保持鍛煉。美國加州大學經濟學教授尤里·格尼茨等人做過一個實驗，他們招募一些學生，把他們分為兩組，一組是“實驗組”，另一組是“對照組”，如果實驗組的學生一個月內去健身中心健身的次數達到8次，他們就獎勵這些學生100美元，而對照組則不提供獎勵。

正如經濟學家所預料的，實驗組的學生大都乖乖去健身。然而，經濟學家們想弄清激勵機制能否有助于長期習慣的養(yǎng)成，一個月過去之后，不再提供獎勵，情況又會怎樣？

結果令人振奮，即使停止獎勵，實驗組學生去健身的頻率仍然是對照組的兩倍，這些簡單的激勵機制幫助學生克服惰性，形成定期運動的習慣，同時也學會怎樣擠出時間運動。

美國廣播公司的黃金段節(jié)目《生活：博弈》，試圖通過參與者的羞恥感來起到減肥的作用。體態(tài)超胖的參與者必須同意只穿一件比基尼來拍照，接下來的兩個月，對所有未能成功減重15磅的人，都要把他的照片在國家電視臺公開，并登在該節(jié)目的網站上。

Just as the economist predicted,students in the experimental group went to the gym as required. However,the economist wanted to know whether incentives would help people to foster a habit. What would happen if there was no incentive after one month?

The results were encouraging.Students in the experimental group attended the gym twice as often as those in the control group. This simple incentive helped students overcome their laziness and form a habit of regular exercise. They also learned to squeeze in time for exercise.

On ABC Primetime’s Game Theory,they tried to help participants lose weight by making them feel ashamed.Overweight participants agreed to take a photo in a bikini. For those who failed to lose more than 15 pounds over the next two months, the photos would be seen on the TV and the Internet.

The economist said this is the behavior of strategy—they were betting with their future self. You want the future self to eat less and exercise more, while the future self wants to eat ice cream and watch movies. It is the future self that wins most of the time. People always start to take action when it’s too late.

The only way to solve this problem is to change the incentive for the future self so as to change your behavior.The temptation of overeating or overspending is still there, but the possibility of being exposed to an embarrassing moment shuts off the temptation. Avoiding such catastrophic exposure becomes a powerful incentive.

In the end, every participant in the program lost more than 15 pounds except one person who almost did.

Dean Karlan, an economist from Yale University, aspired to lose weight. He signed an agreement with a friend who had the same wish. It was stated that whoever was over 175 pounds would pay the other $1000 for every pound over.

Tyler Cowen, professor of economics at George Mason University, had another suggestion: post a bond with your friend, your spouse, and your exercise partner. Write a check in advance. You lose the money if you don’t exercise according to a prearranged plan with well-defined quantitative goals.

However, Taylor also admitted that too many external incentives could reduce internal motivation. ◆

經濟學家把這種行為歸為“策略行動”，也就是說，他們在和未來的自己博弈，今天的自己想讓未來的自己節(jié)食和運動，而未來的自己想吃雪糕和看電影。但大多數時候總是未來的自己獲勝，人們總是在最后才行動，那可悔之晚矣。

解決這一問題唯一的辦法是，改變對未來自己的激勵，從而改變自己的行為。過度飲食或過度花費的誘惑仍然存在，但令人羞恥的曝光的可能性阻斷這種誘惑。想避免這種災難性的曝光，就成了一種強有力的激勵。

最后所有的減肥節(jié)目參與者都減掉15磅以上，除了 一個人，那個人差點也成功了。

耶魯大學經濟學家迪安·卡爾蘭渴望減肥，他與另一位渴望減肥的朋友簽訂一個合同，如果誰的體重超過175磅，超重的那個人就要按照每磅1000美元的標準付給對方。

美國喬治·梅森大學的經濟學教授泰勒·考文也建議說：你可以向朋友、配偶、運動伙伴等“郵寄保證金”，提前寫好支票，如果自己不按照目標定量做減肥健身，就得把這筆錢送給對方。

不過泰勒也承認，太多的外部激勵能夠減少內部動機?！?/p>

經濟學家減肥策略

文/岑嶸 譯/李莉

(From Hangzhou Daily, May 22,2017)

（摘自《杭州日報》2017年5月22日）