Food Cravings: They're All in Your Brain.
From VOA Learning English, this is the Health & Lifestyle report.
We have all been there. It's 3 o'clock and you've been hard at work. As you sit at your desk, a strong desire for chocolate overcomes you. You try to busy yourself to make it go away. But it doesn't. In fact, the more you try to NOT think about a square of deep, dark chocolate melting in your mouth, the more you want it. You can even smell it!
Here is another scenario. Perhaps you are not feeling well. You're coming down with a cold and feel rundown. The only thing you want to eat is a big, bowl of chicken soup, like your mom used to make when you were sick as a child.
A food craving is a strong desire for a specific type of food. And they are normal. Most people have them even though what we crave might be different. One person might crave sweet chocolate, while another might crave salty potato chips.
Sometimes the foods we crave are not super healthy ones but rather fatty or sugary foods. Or sometimes we crave foods from our childhoods, like American meatloaf, Polish pirogues or Vietnamese pho. Other times the cravings may be for something healthy but very specific, such as Japanese sushi or Korean kimchi.
But where do food cravings come from? And how are they different from hunger?
Scientists at the website How Stuff Works compare hunger and cravings this way. Hunger is a fairly simply connection between the stomach and the brain. They even call it simply "stomach hunger."
The website explains that when our stomachs burn up all of the food we have eaten, a hormone (gherlin) sends a message to the one part of the brain, the hypothalamus, for more food. The hypothalamus regulates our most basic body functions such as thirst, hunger and sleep. The brain then releases a chemical to start the appetite. And you eat.
A craving is more complicated. It involves several areas of the brain. These areas make up the reward center of the brain. A craving can also be tied to our mental state and memory. So, some scientists call food cravings "mind hunger."
Scientists add that while hunger is a function of survival, cravings are not. People often crave foods that are high in fat and sugar and not foods that can keep us alive. Foods that are high in fat or high in sugar release chemicals in the brain. These chemicals give us feelings of pleasure and even mild (and temporary) euphoria -- much like a drug.
Back in 2004, researchers at the Monell Chemical Senses Center and the University of Pennsylvania School of Medicine studied food craving and the brain. They used functional magnetic resonance imaging or, fMRI, to show that food cravings activate brain areas related to emotion, memory and reward. These are the same areas of the brain activated during drug-craving studies.
The lead author of this study was Marcia Levin Pelchat, a sensory psychologist. She says that the finding of the study is "consistent with the idea that cravings of all kinds, whether for food, drugs, or designer shoes, have common mechanisms."
They work the same way in the brain. Food cravings, drug addiction, and addictive behaviors such as gambling and over-shopping follow similar neural pathways.
Studies show that our mental state affects our food cravings but not really our hunger levels. Also, our food memories affect what we crave and when. For example, if a child is given sweets when he or she feels sad or upset, that may lead to food cravings for sweets later in life. The reward system in the brain may lead us to seek out familiar pleasures.
In a 2007 study, researchers at Cambridge University found that "dieting or restricted eating generally increase the likelihood of food craving." So, the more you deny yourself a food that you want, they more you may crave it. However, fasting is a bit different. They found that eating no food at all for a short period of time, lessened food cravings.
So, the next time you crave food from your childhood or have a hankering for something very specific, know that your brain may be more to blame than your stomach.
And that's the Health & Lifestyle report.
I'm Anna Matteo.
1.go away 离开；消失
When you go away on holiday, you need to take extra security precautions
2.lead to 导致
A lack of prudence may lead to financial problems.
3.burn up 烧掉
Fires have burned up 180,000 acres of timber.
4.food cravings 对食物的渴求
This may just serve to increase your food cravings, especially in response to emotions.
5.People often crave foods that are high in fat and sugar and not foods that can keep us alive.
keep alive 使...活着；热衷于
I have told you there would be no use for you to keep alive a blind child.
He loved to keep alive the worship of egypt.
6.They found that eating no food at all for a short period of time, lessened food cravings.
a short period of time 短期内
I have never seen such a seismic shift in public opinion in such a short period of time.
How could you do it in such a short period of time?
我们都遇到过这种情况 。已经3点钟了，你一直在努力工作 。坐在办公桌前的你突然产生强烈的欲望：想吃巧克力 。你试着让自己忙碌起来忘掉这件事 。但是丝毫没用 。其实，你越逃避黑巧克力在舌尖融化的幻想，你就越想吃一块 。你甚至能够闻到气味!
再以其他的场景为例 。你可能感觉不舒服 。你感冒了，浑身疲惫 。只想喝一碗热乎的鸡汤，就像小时候生病时妈妈做的鸡汤 。
嘴馋是对某种特定食物的强烈欲望 。这种欲望很正常 。大多数人都会产生这种欲望，只是渴望的食物不同 。有人可能想吃甜巧克力，有人可能想吃咸薯片 。
有时，我们嘴馋的食物并不健康，而是高脂或含糖类食品 。抑或有时，我们也会怀念童年吃过的食物，如美国烘肉卷、波兰pirogue或越南米粉 。甚至有时想吃一些健康又极具特色的饮食如日本寿司或韩国泡菜 。
科学家在《原来如此》（How Stuff Works）网站将饥饿和嘴馋进行了比较 。饥饿是胃和大脑之间一种简单的联系 。可暂且将其称为“肚子饿” 。
该网站解释称，当胃消化完所有的食物时，一种胃肠道激素（gherlin）会向大脑的下丘脑传递信息来获取更多食物 。下丘脑调节人体最基本的身体机能，如口渴、饥饿和睡眠 。然后大脑会释放一种化学物质来唤醒食欲 。之后你就想吃东西了 。
嘴馋更加复杂 。这涉及大脑的数个区域 。这些区域构成了大脑的奖赏中枢 。嘴馋还与人们的精神状态和记忆有关 。因此，有科学家将嘴馋称为“精神饥饿” 。
科学家还指出，饥饿是一种生存功能，而嘴馋则不然 。例如，人们经常想吃的高脂、高糖类食物并不是我们赖以生存的食物 。高脂或高糖类食物会在大脑中释放化学物质 。这些化学物质给人体带来愉悦感，甚至是些许（短暂）快感——像吸毒一样 。
早在2004年，莫奈尔化学感官中心和宾夕法尼亚大学医学院的研究人员就对嘴馋和大脑的关系进行了研究 。他们通过功能性磁共振成像技术（fMRI）发现，嘴馋可以激活与情绪、记忆和奖赏有关的大脑区域 。这些大脑区域与药物渴求研究中显示的区域一样 。
该研究的首席作者是感知心理学家马西娅·列文·佩尔莎 。她表示，这项研究的发现与“多种多样的渴求，无论是对食物、药物还是名牌鞋，都拥有共同机制”的观点是一致的 。
他们在大脑中的工作机制也是一样的 。嘴馋、毒瘾和成瘾性行为，如赌博和过度购物，都遵循相似的神经路径 。
研究表明，人的精神状态会影响其对食物的渴求，但不会影响饥饿程度 。我们对食物的记忆也会影响嘴馋的对象与时间 。例如，如果孩子在悲伤或沮丧时得到糖果，以后可能会对甜食产生渴求 。大脑中的奖赏机制会引导人们寻找似曾相识的愉悦感 。
剑桥大学研究人员在2007年的一项研究中发现，“节食或限制饮食通常会增加嘴馋的可能性 。”因此，你越是抗拒想要的食物，就会越想吃 。不过，禁食就另当别论了 。研究人员发现，短期内不吃任何食物，那么对食物的渴求会下降 。