全世界都在发胖

 当前发达国家和发展中国家都面临肥胖问题的困扰，经济学家夏洛特霍华德对此提出了自己的看法。

三分之二的美国人超重或肥胖。而发展中国家正在迎头赶上。在中国近30％的成年人超重。到2013年，世界各地的决策者们意识到，必须采取行动了。但是，到底该怎么办呢？

这个问题似乎很简单：人们消耗的卡路里太少而摄入的太多。从技术角度上讲，这是一个个人选择问题。我吃油炸圈饼还是去跑步都是可选择的。但是这掩盖了影响体重的那些让人纠结的因素。

人类在演化过程中为能够更好的抵抗饥荒，盐，脂肪和甜食的都变成了十分关键的东西。但是在现代社会，人类的这种生物学特性实在是弊大于利。广告公司花费数十亿美元让人们相信垃圾食品便宜又好吃。美国的含糖饮料从1977年至2001年至少增加了20％的重量。在2011年，平均每个墨西哥人狂饮了728盎司可口可乐，超过其他任何国家。大约30％的墨西哥成年人存在肥胖问题。同时，他们的工作基本没什么体力消耗。汽车减少了步行和骑自行车的机会。在这些大的趋势之下还有些次要因素比如住宅附近是否有操场，学校能否提供合适的午餐，父母是否有时间准备饭菜，在热量和运动之间人们似乎无可救药地偏向了前者。

“经济学家”的饮食

这对卫生系统和库房构成了严重的挑战。肥胖会增加心血管疾病、糖尿病、肝病、关节炎和某些癌症的风险。令人担忧的是，亚洲人在比西方人轻的情况下就会出现健康问题了。据医学研究所估计，在美国，与肥胖有关的疾病的费用一年约190亿美元，占卫生支出的五分之一。在发展中国家，肥胖可能限制经济增长，因为这样的工人生产效率低，还会加大卫生系统的负担。

有一种说法是无为而治。如果一个人是胖的，就随他（她）去吧。约翰·斯图亚特·穆勒说，如果一个人的行为伤害的不只是他自己，那么国家就可能会进行干预。但在富裕国家，医疗费用很高而且通常是由纳税人集体承担的。肥胖者会因为穆勒的测试而尖叫。

第二个说法是惩罚那些超重的人。日本已经对公民的腰围制定了具体的标准。如果工人不瘦下来，他们的雇主将面临罚款。这就有点过份了。减肥是很困难了，因为荷尔蒙是不断变化的。人可能因为多种原因发胖，包括他们的童年，他们的工作，这不是他们的错。

政府也应该考虑大幅对苏打水加税

第三个说法是比较中庸的“软性家长主义”受到行为经济学家的青睐。这种想法是不限制人的选择，而是诱使其选择胡萝卜而不是薯条。纽约市长迈克尔·布隆伯格，他选择了从软到硬的家长式作风：他的大碳酸饮料瓶销售禁令将于2013年3月生效。

正确的政策组合应该是怎样的呢？这儿有对于来年的一些建议（人称“经济学家”菜谱）。政府不应该强迫人们吃西兰花，但他们可以改变的补贴政策使西兰花更便宜。他们可以确保学校午餐是健康的，孩子们有时间到处跑。他们可以设置明确的营养标准，受过教育的消费者会明智地购物，并要求健康的产品。政府也应考虑对汽水征收重税。糖浆状的东西是肥胖的主要驱动力，不像汉堡包，它完全没有营养价值。一种税，不至于侵犯个人的自由，就像强迫他系安全带一样。

关于政府是否应该迫使企业做出更健康的食品还有待考虑。公司正试图抵御政府干预，例如通过降低食盐摄取量。2010年，公司承诺从他们的美国产品五年内削减15000亿卡路里的热量。第一份进度报告将在2013年发表。不过需要注意的是，公司们在西方正尽量让食品更健康，但他们依然在其他地方兜售垃圾食品。
Two-thirds of Americans are overweight or obese. Developing countries are catching up. In China nearly 30% of adults are too wide. In 2013 policymakers around the world will realise that something must be done. But what, exactly?

The problem seems simple: people consume more calories than they spend. Technically, reversing this is a matter of individual choice. Do I eat the doughnut or go for a run? But this masks the tangle of factors that influence weight.

People have evolved to favour salt, fat and sweets, gobbling as much as possible to store energy should they encounter famine. But human biology is ill-suited for the modern world. Junk food is cheap and delicious; firms spend billions advertising it. In America sugary drinks accounted for at least 20% of the weight gained from 1977 to 2001. In 2011 the average Mexican guzzled 728 eight-ounce servings of Coca-Cola, more than in any other country. About 30% of Mexican adults are obese. Meanwhile jobs require less physical exertion. Cars have reduced the need for walking and cycling. Add to these big trends a host of smaller factors—are there playgrounds nearby, do schools serve proper lunches, do parents have time to prepare meals?—and the balance between calories and exercise seems hopelessly tilted towards the former.

The Economist diet

This poses a grave challenge to health systems and public coffers. Obesity increases the risk of cardiovascular disease, diabetes, liver disease, joint troubles and some cancers. Worryingly, Asians develop health problems at lower weights than their Western counterparts. In America, obesity-related illnesses cost around $190 billion a year, or one-fifth of health spending, reckons the Institute of Medicine. In developing countries, obesity threatens to limit growth, as workers become less productive and wobbly health systems buckle under new demand.

One response is to do nothing. If an individual is fat, so be it. John Stuart Mill said the state may intervene only if a man’s actions harm not just himself but others. But medical costs are high and, in rich countries, are usually borne by taxpayers. Obesity squeaks by Mill’s test.

A second response is to punish those who are overweight. Japan has set a specific limit to citizens’ waistlines. If workers do not slim down, their employers face fines. This is overreach. Weight is hard to lose, and keep off, because of hormonal changes. And people may be fat for reasons—including their childhood and their work—which are not their fault.

A third response is somewhere in the middle: the “soft paternalism” favoured by behavioural economists. The idea is not to limit choice, but to make it easier for individuals to choose carrots over French fries. New York’s mayor, Michael Bloomberg, is veering from soft to hard paternalism: his ban on the sale of big soda bottles is due to take effect in March 2013.

What’s the right policy mix? Here’s some advice for the year ahead (call it The Economist diet). Governments should not force people to eat broccoli, but they can certainly change subsidies to make broccoli cheaper. They can ensure that school lunches are healthy and that children have time to run around. They can set clear standards for nutrition labels, so that educated consumers will shop wisely and demand healthier products. Governments should also consider imposing a hefty tax on soda. The syrupy stuff is a main driver of obesity and, unlike a hamburger, has no nutritional value. A soda tax is far less intrusive of an individual’s liberty than, say, forcing him to wear a seat belt.

More questionable is whether governments should force companies to make healthier food. Firms are trying to fend off intervention by acting first, for example by reducing salt. In 2010 companies promised to cut 1.5 trillion calories from their American offerings within five years. The first progress report will be published in 2013. Watch out, though, for firms that make food healthier in the West but keep peddling junk elsewhere.