经济学家减肥策略

文 / 岑嵘 译 / 李莉

Special Focus - - Inspiration -

美国一项针对腰围的研究发现:从 1970年左右开始,我们身体每天的能耗就基本维持在一个稳定的水平,但人们的食量开始增长,每过十年,我们的日均能量摄入量增长300 千焦,于是肥胖成为一个困扰现代人的重大问题。

经济学家们发现,更大的盘子、碗甚至是食品柜,都会增大我们的食量。

在一项实验中,研究者把一些存放 14天的爆米花,装在不同规格的桶中分给电影观众,结果拿大桶爆米花的观众,比其他人多吃下38%的过期爆米花。这说明人们往往根据外部信息(我的盘子空了),而非内部信息(我饱了)停止进食。

在另一项实验中,他们把10条减肥策略随机分配给实验参与者,最终他们发现最成功的两条减肥策略:坚持用小盘子(直径小于 25厘米)进食的参与者,一个月内平均减掉0.9 公斤;吃饭时禁止看电视的实验者,一个月内平均减掉0.7 公斤。

康奈尔大学食物与品牌实验室主任布莱恩·万辛克发现:看悲伤的电影会让你多吃28% 至55%的东西;餐厅中柔和的灯光和动听的爵士乐会让你吃得更少;所持餐盘的颜色与盘中食物的颜色色差较小,会让人多吃 22%至 32%的食物。

除了控制食欲,减肥的另一个关键是健身。经济学家试图通过激励机制让人们保持锻炼。美国加州大学经济学教授尤里·格尼茨等人做过一个实验,他们招募一些学生,把他们分为两组,一组是“实验组”,另一组是“对照组”,如果实验组的学生一个月内去健身中心健身的次数达到 8 次,他们就奖励这些学生 100 美元,而对照组则不提供奖励。

正如经济学家所预料的,实验组的学生大都乖乖去健身。然而,经济学家们想弄清激励机制能否有助于长期习惯的养成,一个月过去之后,不再提供奖励,情况又会怎样?

结果令人振奋,即使停止奖励,实验组学生去健身的频率仍然是对照组的两倍,这些简单的激励机制帮助学生克服惰性,形成定期运动的习惯,同时也学会怎样挤出时间运动。

美国广播公司的黄金段节目《生活:博弈》,试图通过

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.

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 GameThe­ory , 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. t

( From HangzhouDaily , May 22,

2017)

参与者的羞耻感来起到减肥的作用。体态超胖的参与者必须同意只穿一件比基尼来拍照,接下来的两个月,对所有未能成功减重 15 磅的人,都要把他的照片在国家电视台公开,并登在该节目的网站上。

经济学家把这种行为归为“策略行动”,也就是说,他们在和未来的自己博弈,今天的自己想让未来的自己节食和运动,而未来的自己想吃雪糕和看电影。但大多数时候总是未来的自己获胜,人们总是在最后才行动,那可悔之晚矣。

解决这一问题唯一的办法是,改变对未来自己的激励,从而改变自己的行为。过度饮食或过度花费的诱惑仍然存在,但令人羞耻的曝光的可能性阻断这种诱惑。想避免这种灾难性的曝光,就成了一种强有力的激励。

最后所有的减肥节目参与者都减掉 15 磅以上,除了 一个人,那个人差点也成功了。

耶鲁大学经济学家迪安·卡尔兰渴望减肥,他与另一位渴望减肥的朋友签订一个合同,如果谁的体重超过 175 磅,超重的那个人就要按照每磅1000美元的标准付给对方。

美国乔治·梅森大学的经济学教授泰勒·考文也建议说:你可以向朋友、配偶、运动伙伴等“邮寄保证金”,提前写好支票,如果自己不按照目标定量做减肥健身,就得把这笔钱送给对方。

不过泰勒也承认,太多的外部激励能够减少内部动机。

(摘自《杭州日报》2017 年 5月 22 日)

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