为什么青少年更难抗拒垃圾食品？

Why Is It Harder for Teenagers to Resist Junk Food？

It’s hard to turn down hamburgers， French fries， potato chips and all of the other junk food that seem to call out to us. However， eating too much junk food can harm your body， particularly if you’re between the ages of 10 and 19.

“Junk food shapes adolescent brains in ways that impair their ability to think， learn and remember. It can also make it harder to control impulsive behaviors，” said Amy Reichelt， a brain and nutrition specialist at Western University， Canada. “It may even up a teen’s risk of depression and anxiety.”

Reichelt and two other researchers reviewed more than 100 studies， including their own， about how poor food choices can impact adolescent brains. They found adolescents are more sensitive than any other age group to processed foods with a lot of fat and sugar as their brains are not yet fully formed.

Adolescent brains are still developing the ability to assess risks and control actions. The prefrontal cortex is the part of the brain that tells us we shouldn’t eat chips all the time and helps us resist that urge. However， this region is the last to mature — it doesn’t fully develop until we are in our early 20s.

我们很难拒绝汉堡、薯条、薯片和其他所有似乎在召唤着我们的垃圾食品。然而，吃太多垃圾食品会对身体造成伤害，尤其是对于10到19岁的青少年。

“垃圾食品会损害思维、学习、记忆能力，进而影响青少年的大脑发育。它还会让人更难以控制冲动行为。”加拿大韦仕敦大学的脑部和营养学专家艾米·瑞切特说，“垃圾食品甚至可能会增加青少年患抑郁症和焦虑症的风险。”

瑞切特和其他两名研究人员回顾了包括他们自己的研究在内的100多项关于不良的食物选择会如何影响青少年大脑的研究。他们发现，相比其他年龄段的人群，青少年对高脂高糖的加工食品更为敏感，因为他们的大脑尚未发育完全。

青少年大脑的评估风险和控制行为的能力尚在发育。大脑中的前額皮质会告诉我们，不应该总吃薯片，并帮助我们抗拒这种强烈的欲望。然而，这一区域是最后发育成熟的部分——要到20出头才发育完全。

你是否也知道垃圾食品不健康，但就是管不住嘴？科学家最新研究表明，垃圾食品会对大脑造成负面影响，造成记忆减退，认知能力下降，而且对青少年的影响尤为明显。

Meanwhile， teen brains get more buzz from rewards. The parts of the brain that make us feel good when we do something pleasurable—like eating tasty foods—are fully developed by the teen years.

In fact， these regions are even more sensitive when we are young. That’s because dopamine， a natural chemical that lifts our mood when we experience something good， is especially active in adolescent brains.

Therefore， the teen brain has two strikes against it when it comes to resisting junk food. “It has a heightened drive for rewards and reduced self-regulation，” said Reichelt.

Reichelt and her team conducted their own study using mice， whose brains develop much like our own. They discovered that the “teenage” mice that had a high-fat diet performed worse on memory tests than those eating a normal diet. Researchers said the high-fat diet may make the mice’s prefrontal cortex work less effectively.

So， what’s the best way to say no to junk food？ Researchers suggest exercise. When we exercise， the brain’s reward system becomes less sensitive to food cues. Exercise also triggers the body to make a protein that helps brain cells grow and boosts connections between the prefrontal cortex and other brain regions. The prefrontal cortex thus can work better to help us make wise decisions and control our impulses.

与此同时，青少年的大脑在得到奖励后会更为兴奋。当我们做了些愉快的事——比如，吃到了美味的食物，能让我们感到快乐的这部分大脑区域，要到十几岁才能发育完全。

实际上，我们年轻时这些区域甚至会更加敏感。那是因为多巴胺在青少年的大脑中尤为活跃，它是一种天然的化学物质，会在我们遇到好事时使我们心情愉悦。

因此，抵抗垃圾食品时，青少年的大脑会处于双重劣势之下。“大脑更想要获得奖励，并降低了自我调节能力。”瑞切特表示。

瑞切特和她的团队利用老鼠进行了他们的研究，这些老鼠的大脑发育与人类十分相似。他们发现，在记忆测试中，摄入高脂食物的“青少年”老鼠，表现得不如正常饮食的老鼠。研究人员称，高脂饮食可能会使老鼠的前额皮质降低工作效率。

那么，对垃圾食品说“不”的最佳方式是什么呢？研究人员的建议是锻炼。当我们锻炼时，大脑的奖励系统对食物信号的敏感度会降低。锻炼还能促使身体产生一种蛋白质，这种蛋白质有助于脑细胞的生长，增强前额皮质与大脑其他区域之间的联系。因此，前额皮质能更好地帮助我们做出明智的选择，控制我们的冲动。

Word Study

impair /ɪm'peə（r）/ v. 损害;削弱

Even one drink can impair driving performance.

impact /ɪm'pækt/ v. （對某事物）有影响;有作用

n. 巨大影响;强大作用

Her father’s death impacted greatly on her childhood years.

Her speech made a deep impact on everyone.

resist /rɪ'zɪst/ v. 抵制;阻挡

boost /buːst/ v. 使增长;增强;促进

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