Deborah Cohen is a senior natural scientist at the Rand Corp. and the author of the forthcoming book “A Big Fat Crisis: The Hidden Forces Behind the Obesity Epidemic and How We Can End It。”

The obesity epidemic is among the most critical health issues facing the United States. Although it has generated a lot of attention and calls for solutions, it also has served up a super-sized portion of myths and misunderstandings。

1.If you’re obese, blame your genes。

As obesity rates have soared, some researchers have focused on individuals’ genetic predisposition for gaining weight. Yet, between 1980 and 2000, the number of Americans who are obese has doubled — too quickly for genetic factors to be responsible。

So why do we eat more than we need? The simple answer: Because we can. At home and at restaurants, a dollar puts more calories on our plates than ever before. Before World War II, the average family spent as much as 25 percent of its total income on food — in 2011, it was 9.8 percent. And people eat out now more than in the past. In 1966, the average family spent 31 percent of its food budget dining away from home — in 2011, it was 49 percent. Because restaurant meals usually have more calories than what we prepare at home, people who eat out more frequently have higher rates of obesity than those who eat out less。

Meanwhile, the food industry has developed tens of thousands of products with more calories per bite, as well as new, effective marketing strategies to encourage us to buy and consume more than necessary. We should blame these business practices, which are modifiable, for obesity rather than our genes, which are not。

2.If you’re obese, you lack self-control。

According to a 2006 study, “research on restrained eating has proven that in most circumstances dieting is not a feasible strategy。” In other words: People won’t lose weight by trying to eat less because they can’t easily control themselves. Unfortunately, this puritanical view of personal resolve plays down how our surroundings and mental state determine what we eat。

Research shows that if we are overwhelmed with too much information or preoccupied, we have a tendency to surrender to poor dietary choices. In one study, for example, people asked to choose a snack after memorizing a seven-digit number were 50 percent more likely to choose chocolate cake over fruit salad than those who had to memorize a two-digit number. When adults in another study were asked to sample a variety of foods after watching a television show with junk-food commercials, they ate more and spent a longer time eating than a similar group watching the same show without the junk-food ads. In the same study, children ate more goldfish crackers when watching junk-food commercials than those who saw other ads。

Our world has become so rich in temptation that we can be led to consume too much in ways we can’t understand. Even the most vigilant may not be up to the task of controlling their impulses。

3. Lack of access to fresh fruits and vegetables is responsible for the obesity epidemic。

The Obama administration’s Healthy Food Financing Initiative is meant to help low-income communities that lack access to fresh food. Although the U.S Department of Agriculture estimates that fewer than 5 percent of Americans live in these “food deserts,” about 65 percent of the nation’s population is overweight or obese. For most of us, obesity is not related to access to more nutritious foods, but rather to the choices we make in convenience stores and supermarkets where junk-food marketing dominates. Since we are buying more calories than we need, eating healthfully could be made more affordable by eliminating unnecessary cheaper low nutrient foods and substituting higher quality foods that may be slightly more expensive。

Obesity is usually the consequence of eating too much junk food and consuming portions that are too large. People may head to the produce section of their grocery store with the best intentions, only to be confronted by candy at the cash register and chips and soda at the end of aisles. Approximately 30 percent of supermarket sales are from such end-of-aisle locations. Food retailers’ impulse-marketing strategies contribute significantly to obesity across the population, not just for those who do not live near a green grocer or can’t afford sometimes pricier healthy choices。

4. The problem is not that we eat too much, but that we are too sedentary。

First lady Michelle Obama’s “Let’s Move” campaign is based on the idea that if kids exercised more, childhood obesity rates would decline. But according to the Centers for Disease Control and Prevention, there was no significant decrease in physical activity levels as obesity rates climbed in the 1980s and 1990s. In fact, although a drop in work-related physical activity may account for up to 100 fewer calories burned, leisure physical activity appears to have increased, and Americans keep tipping the scales。

There is compelling evidence that the increase in calories consumed explains the rise in obesity. The National Health and Nutrition Examination found that people take in, on average, more than 500 more calories per day now than they did in the late 1970s, before obesity rates accelerated.That’s like having Christmas

dinner twice a week or more. It wouldn’t be a problem if we stuffed ourselves only once a year, but all-you-can-eat feasts are now available all the time. It’s nearly impossible for most of us to exercise enough to burn off these excess calories。

5. We can conquer obesity through better education about diet and nutrition.. We can conquer obesity through better education about diet and nutrition。

According to a physicians’ health study, 44 percent of male doctors are overweight. A study by the University of Maryland School of Nursing found that 55 percent of nurses surveyed were overweight or obese. If people who provide health care cannot control their weight, why would nutrition education alone make a difference for others?

Even with more information about food, extra-large portions and sophisticated marketing messages undermine our ability to limit how much we consume. Consider Americans’ alcohol consumption: Only licensed establishments can sell spirits to people older than 21, and no alcohol can be sold in vending machines. Yet there are very few standards or regulations to protect Americans from overeating。

In the 19th century, when there were no controls on the quality of drinking water, infectious disease was a major cause of death. Once standards were established, the number of these fatalities plummeted。

Similarly, if Americans did not live in a world filled with buffets, cheap fast food, soft drinks with corn syrup, and too many foods with excess fat, salt and sugar, the incidence of obesity, heart disease, high blood pressure and diabetes probably would plummet. Education can help, but what’s really needed is regulation — for example, limits on marketing that caters to our addiction to sugar and fat。

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黛博拉•科恩是美國蘭德公司一位高級自然科學家，她所著書籍《肥胖危機：肥胖背后隱藏的原因及如何擺脫肥胖》即將出版問世。

肥胖癥是美國人面臨的最嚴峻的健康問題之一。盡管它已經(jīng)引起了廣泛關注和對治療辦法的訴求，人們對于肥胖癥的理解仍然有超大比例的謬見和誤解：

1.肥胖癥來自于基因

隨著肥胖癥比率的飆升，一些研究者開始關注個人基因素質(zhì)對體重增加的影響。然而，從1980年到2000年，美國肥胖癥患者數(shù)增加了一倍——基因影響無法導致如此快的增長速度。

那為什么我們會攝入超出需求量的食物?答案很簡單，因為我們的經(jīng)濟條件允許。在家或者在餐廳，1美元較之以前能將更多的卡路里放入餐盤。二戰(zhàn)前，平均每個家庭在食物上花費總收入的25%——而在2011年，只有9.8%。人們現(xiàn)在也比以前更多地外出就餐。1966年，平均每個家庭外出就餐的花費占總食物支出預算的31%——而在2011年，比例達到49%。由于餐廳提供的食物比家里準備的富含更多卡路里，頻繁外出就餐的人就比其他人有更高的風險患上肥胖癥。

與此同時，食品工業(yè)生產(chǎn)出數(shù)以萬計的產(chǎn)品，每一口都有更多的卡路里含量;新型高效的市場營銷戰(zhàn)略也誘使我們購買、消費超出需求的食物。比起改變不了的基因，我們更應該歸咎于這些商業(yè)活動，畢竟它們可以為解決肥胖問題做出一些改變。

2. 肥胖癥來自于自制力的缺乏

2006年的一項研究顯示，“關于節(jié)制飲食的調(diào)查已經(jīng)證明，在大多數(shù)情況下節(jié)食并不是切實可行的減肥策略。”換句話說，由于人們不能輕易控制自己，吃得少并不能使體重減輕。不幸的是，這種清教徒式的個人決心使得周圍環(huán)境和精神狀態(tài)對“吃什么”的決定作用大為減輕。

研究表明如果我們被過多信息淹沒或者全神貫注做某事時，我們會傾向于向食物投降。舉例來說，在一次研究中，熟記過一個7位數(shù)的受試者在被要求選擇零食時，選擇巧克力蛋糕而不是水果沙拉的幾率要比那些熟記過一個2位數(shù)的受試者高出50%。在另一項研究中，一組成年人在觀看過插播有垃圾食品廣告的電視節(jié)目后被要求選取各種食物，另外一組成年人觀看沒有廣告的相同電視節(jié)目，最后第一組成年人在觀看后吃得更多、更久。另外，同一項研究還發(fā)現(xiàn)，觀看垃圾食品廣告的兒童比那些看其他廣告的吃了更多金魚餅干。

我們生活的世界充滿了誘惑，它誘導我們以自身都無法理解的方式過度消費。即使最警惕的人也無法成功控制他們的沖動。

3.肥胖癥是因為缺少獲得新鮮水果蔬菜的渠道

奧巴馬政府的健康食品融資計劃旨在幫助那些無法獲取新鮮食物的低收入群體。不過據(jù)美國農(nóng)業(yè)部估計，只有不到5%的美國人生活在這樣的“食物荒漠”中，約65%的美國人肥胖超重。對于我們大多數(shù)人來說，肥胖癥跟是否能獲取有營養(yǎng)的食物無關，而是跟我們在以垃圾食品為主導市場的便利店或超市做出的購買決定有關。由于我們總是買超出需求的卡路里，因此清除那些不必要的低價格、低營養(yǎng)的食物，用高品質(zhì)、稍昂貴點的食物代替，會使我們能夠更加實惠地健康飲食。

肥胖通常是由于消費、食用過多垃圾食品導致的。人們可以懷著美好的意圖走向雜貨店的農(nóng)產(chǎn)品區(qū)，不過他們必須面對收銀臺旁邊的糖果和過道拐角處的薯片、蘇打水。而在超市里大約有30%的商品是被擺放在過道盡頭之類的位置。食品零售商們的促銷策略顯著增加了全部人口的肥胖率，而不僅僅是那些居住遠離綠色食品或不能支付偶爾高價的健康食品的人。

4. 肥胖癥的關鍵問題不是吃得太多，而是坐得太久。

美國第一夫人米歇爾•奧巴馬發(fā)起的“動起來”活動基于這樣一個觀點：如果孩子們更多地鍛煉，那么兒童肥胖率就會下降。

但是美國疾病控制與預防中心的資料顯示，上世紀80、90年代的體育鍛煉水平并沒有顯著降低，但肥胖率卻有所攀升。其實盡管不做專門的體育運動會減少100卡路里的燃燒，但是一些休閑日�；顒尤阅茉黾涌�路里的燃燒，而美國人卻在持續(xù)增重。

有令人信服的證據(jù)表明卡路里消耗量的增加解釋了肥胖癥越來越多的原因。國家健康與營養(yǎng)調(diào)查發(fā)現(xiàn)，與上世紀70年代肥胖癥患病率還未增加時相比，人們平均每天會多攝入超過500單位的卡路里。這就相當于我們每周超過兩次吃圣誕大餐。如果我們每年僅有一次塞滿自己的胃，肥胖就不是問題。但是現(xiàn)在隨處隨時都可以吃大餐了。得到足夠鍛煉來消耗完過剩的卡路里，對我們大多數(shù)人來說也是幾乎不可能的。

5. 我們可以通過更好的飲食與營養(yǎng)教育來戰(zhàn)勝肥胖。

一名內(nèi)科醫(yī)生的健康研究結(jié)果顯示，44%的男性醫(yī)生體重超標。而馬里蘭護理大學的一項研究發(fā)現(xiàn)接受調(diào)查的護士中有55%超重或肥胖。如果那些提供衛(wèi)生保健的人不能控制好自己的體重，又怎么能單靠營養(yǎng)教育來幫助減輕其他人的體重呢?

即使我們更了解食物本身、過大的食物支出比例和復雜的市場營銷，它們?nèi)匀幌魅趿宋覀兿拗葡�費的能力。試想美國的酒精消費情況：只有那些授權機構(gòu)可以把烈性酒賣給超過21歲的人，自動售貨機不得出售任何酒精。但是美國現(xiàn)在幾乎沒有限制人們暴飲暴食的標準或規(guī)定。

十九世紀時人們還沒有對飲水質(zhì)量采取控制措施，傳染病是死亡的主要原因。水質(zhì)標準被建立起來后，死亡人數(shù)驟降。

類似地，如果美國人民沒有生活在充滿自助餐、廉價快餐、玉米糖漿飲料，還有過多含有過量脂肪、鹽分和糖的食物的世界里，肥胖癥、心臟病、高血壓和糖尿病的發(fā)病率可能就會驟降。營養(yǎng)教育很有用，但我們更需要的是規(guī)章制度——比如，限制銷售為迎合大眾對糖類、脂肪依賴心理的食物。