爲什麼大腦忙起來人就容易餓

A busy brain can mean a hungry body.

大腦忙碌可能會導致身體飢餓。

We often seek food after focused mental activity, like preparing for an exam or poring over spreadsheets.

我們經常在集中進行腦力活動後尋找食物，比如備考或閱讀報表。

Researchers speculate that heavy bouts of thinking drain energy from the brain, whose capacity to store fuel is very limited.

研究者猜測，高強度思考會耗盡腦部能量，而腦部存儲養分的能力十分有限。

So the brain, sensing that it may soon require more calories to keep going, apparently stimulates bodily hunger, and even though there has been little in the way of physical movement or caloric expenditure, we eat.

所以，大腦感覺自己可能很快就需要更多熱量來維持運轉，顯然會因此刺激身體產生飢餓感。儘管幾乎沒有進行體力運動或出現熱量消耗，我們還是會吃東西。

This process may partly account for the weight gain so commonly seen in college students.

這個過程可以部分解釋大學生中常見的體重增加現象。

Scientists at the University of Alabama at Birmingham and another institution recently experimented with exercise to counter such post--study food binges.

前不久，亞拉巴馬大學伯明翰分校(University of Alabama at Birmingham)的科學家們和另一個研究機構試驗通過運動對抗學習後的暴飲暴食。

Gary Hunter, an exercise physiologist at U.A.B., oversaw the study, which was published this month in the journal Medicine & Science in Sports & Exercise.

這項研究由亞拉巴馬大學伯明翰分校的運動生理學家加里•亨特(Gary Hunter)主持，本月發表在《體育醫學與科學》(Medicine & Science in Sports & Exercise)上。

Hunter notes that strenuous activity both increases the amount of blood sugar and lactate — a byproduct of intense muscle contractions — circulating in the blood and augments blood flow to the head.

亨特指出，劇烈活動會增加在血液中循環的血糖和乳酸鹽含量——這是肌肉劇烈收縮的副作用——增加腦部的血流量。

Because the brain uses sugar and lactate as fuel, researchers wondered if the increased flow of fuel-rich blood during exercise could feed an exhausted brain and reduce the urge to overeat.

大腦以糖和乳酸鹽爲養料，所以研究者們想知道，鍛鍊中增加的養料豐富的血流量是否能給疲憊的大腦提供養分，從而減輕過度進食的衝動。

Thirty--eight healthy college students were invited to U.A.B.’s exercise lab to determine their fitness and metabolic rates — and to report what their favorite pizza was.

38名健康的大學生被邀請到亞拉巴馬大學伯明翰分校的運動實驗室，接受健康水平和代謝率檢測，並報告自己最喜歡吃哪種披薩。

Afterward, they sat quietly for 35 minutes before being given as much of their favorite pizza as they wanted, which established a baseline measure of self--indulgence.

之後，他們靜坐35分鐘，然後他們想吃多少披薩就供應多少，以確定自我放縱的基線。

At a later date, the volunteers returned and spent 20 minutes tackling selections from college and graduate--school entrance exams.

在後來的一個日子裏，志願者們返回這裏，花費20分鐘時間做從大學和研究生入學考試中挑選的題目。

Hunter says this work has been used in other studies to induce mental fatigue and hunger.

亨特說，這種方法已經在其他研究中被用於引發精神疲勞和飢餓感。

Next, half the students sat quietly for 15 minutes, before being given pizza.

接下來，其中一半學生靜坐15分鐘，然後進食披薩。

The rest of the volunteers spent those 15 minutes doing intervals on a treadmill: two minutes of hard running followed by about one minute of walking, repeated five times.

剩下的志願者用那15分鐘時間在跑步機上做運動：快跑2分鐘，然後走大約1分鐘，重複5次。

This is the sort of brief but intensive routine, Hunter says, that should prompt the release of sugar and lactate into the bloodstream.

亨特說，這種短暫而高強度的運動應該能促進糖和乳酸鹽釋放到血流中。

These students were then allowed to gorge on pizza, too.

這些學生之後也被允許盡情食用披薩。

But by and large, they did not overeat.

總體來說，他們沒有過量進食。

In fact, the researchers calculated that the exercisers consumed about 25 fewer calories than they did during their baseline session.

實際上，研究者們計算出，這些鍛鍊者攝入的熱量比在基線測試階段大約少25卡路里。

The nonexercisers, however, consumed about 100 calories more.

但是，那些沒有鍛鍊的人大約多攝入了100卡路里。

When the researchers factored in the calories expended on running, they determined that those students actually consumed 200 fewer total calories after their brain workouts than the resting students.

研究者們把跑步中耗費的熱量計算在內後發現，那些學生實際上在腦力活動後比其他學生一共少攝入200卡路里。

The study has limitations, of course.

這項研究當然具有侷限性。

We only looked at lunch, Hunter says; the researchers do not know if the runners consumed extra calories at dinner.

我們只研究了午餐，亨特說。研究者不知道跑步者在晚餐時是否攝入了更多熱量。

They also cannot tell whether other types of exercise would have the same effect as running, although Hunter says they suspect that if an activity causes someone to break into a sweat, it should also increase blood sugar and lactate, feeding the brain and weakening hunger’s call.

他們也不知道其他哪些運動會收到和跑步一樣的效果，不過亨特說，他們猜測，如果一項運動能讓人出汗，那麼它應該也能增加血糖和乳酸鹽釋放，給大腦提供養分，從而緩解飢餓感。