為什么青少年更難抗拒垃圾食品？

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.

我們很難拒絕漢堡、薯條、薯片和其他所有似乎在召喚著我們的垃圾食品。然而，吃太多垃圾食品會對身體造成傷害，尤其是對于10到19歲的青少年。

“垃圾食品會損害思維、學(xué)習(xí)、記憶能力，進而影響青少年的大腦發(fā)育。它還會讓人更難以控制沖動行為。”加拿大韋仕敦大學(xué)的腦部和營養(yǎng)學(xué)專家艾米·瑞切特說，“垃圾食品甚至可能會增加青少年患抑郁癥和焦慮癥的風(fēng)險。”

瑞切特和其他兩名研究人員回顧了包括他們自己的研究在內(nèi)的100多項關(guān)于不良的食物選擇會如何影響青少年大腦的研究。他們發(fā)現(xiàn)，相比其他年齡段的人群，青少年對高脂高糖的加工食品更為敏感，因為他們的大腦尚未發(fā)育完全。

青少年大腦的評估風(fēng)險和控制行為的能力尚在發(fā)育。大腦中的前額皮質(zhì)會告訴我們，不應(yīng)該總吃薯片，并幫助我們抗拒這種強烈的欲望。然而，這一區(qū)域是最后發(fā)育成熟的部分——要到20出頭才發(fā)育完全。

你是否也知道垃圾食品不健康，但就是管不住嘴？科學(xué)家最新研究表明，垃圾食品會對大腦造成負面影響，造成記憶減退，認知能力下降，而且對青少年的影響尤為明顯。

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.

與此同時，青少年的大腦在得到獎勵后會更為興奮。當(dāng)我們做了些愉快的事——比如，吃到了美味的食物，能讓我們感到快樂的這部分大腦區(qū)域，要到十幾歲才能發(fā)育完全。

實際上，我們年輕時這些區(qū)域甚至?xí)用舾小Ｄ鞘且驗槎喟桶吩谇嗌倌甑拇竽X中尤為活躍，它是一種天然的化學(xué)物質(zhì)，會在我們遇到好事時使我們心情愉悅。

因此，抵抗垃圾食品時，青少年的大腦會處于雙重劣勢之下。“大腦更想要獲得獎勵，并降低了自我調(diào)節(jié)能力。”瑞切特表示。

瑞切特和她的團隊利用老鼠進行了他們的研究，這些老鼠的大腦發(fā)育與人類十分相似。他們發(fā)現(xiàn)，在記憶測試中，攝入高脂食物的“青少年”老鼠，表現(xiàn)得不如正常飲食的老鼠。研究人員稱，高脂飲食可能會使老鼠的前額皮質(zhì)降低工作效率。

那么，對垃圾食品說“不”的最佳方式是什么呢？研究人員的建議是鍛煉。當(dāng)我們鍛煉時，大腦的獎勵系統(tǒng)對食物信號的敏感度會降低。鍛煉還能促使身體產(chǎn)生一種蛋白質(zhì)，這種蛋白質(zhì)有助于腦細胞的生長，增強前額皮質(zhì)與大腦其他區(qū)域之間的聯(lián)系。因此，前額皮質(zhì)能更好地幫助我們做出明智的選擇，控制我們的沖動。

Word Study

impair /?m'pe?（r）/ v. 損害;削弱

Even one drink can impair driving performance.

impact /?m'p?kt/ v. （對某事物）有影響;有作用

n. 巨大影響;強大作用

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

Her speech made a deep impact on everyone.

resist /r?'z?st/ v. 抵制;阻擋

boost /bu?st/ v. 使增長;增強;促進

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