Under normal circumstances, we feel hungry when we have burnt up the food we have eaten as energy and our blood sugar and insulin levels begin to drop. Ghrelin, a hormone connected to appetite, then communicates this to the brain, which is how we feel the need to eat.

But all sorts of things can interfere with this process.

According to a 2011 study by researchers at Columbia University in the United States, those who are sleep-deprived eat almost 300 calories a day more than those who get enough sleep.

This is because levels of the hormone ghrelin, which tells the brain we need to eat, increase when we don’t get enough sleep.

The Columbia researchers noted that the women who didn’t get enough sleep took in more fat by around 30 grams on sleep-deprived days — four times as much as the average increase for men.

In a 2013 study, people who were primed to expect “tough times ahead” ate more food than people who listened to neutral messages.

It’s thought that hearing about troubled times causes a survival instinct to kick in, leading to cravings for high-calorie snacks such as chocolate.

Tempted by that extra biscuit? Then just enjoy it. Researchers have found that when you feel guilty about a pleasurable experience, the guilt itself becomes pleasurable, encouraging you to do it more.

“If we consider something a naughty pleasure, it can psychologically drive the appetite and the guilt may make you want to eat more,” says Cary Cooper, at the University of Lancaster.

The appetite center of the brain also lies very close to the area governing mood — the limbic system — which is why changes in the way we feel may affect appetite.

The bright blue light emitted by devices such as smartphones and tablets may also give an unwelcome boost to your appetite.

Research this year found that a person’s appetite continues to increase when he or she is exposed to the light.

It also altered people’s metabolism, as blood tests showed that the blue-light subjects had higher insulin and glucose levels.

One possible explanation is that bright blue light at night confuses our body clock, which has a role in controlling when we feel the need to eat.

Words to Learn 相关词汇

【胰岛素】yídǎosù insulin a protein hormone, secreted in the pancreas by the islets of Langerhans, that controls the concentration of glucose in the blood

【边缘叶的】biānyuányè de limbic pertaining to or of the nature of a limbus or border, marginal

在正常情况下，当身体把食物转为能量消耗掉之后，我们的血糖和胰岛素水平也开始降低，这时我们就会感到饥饿。然后，饥饿激素将这个信息传达给大脑。这样我们就会感觉到需要吃东西了。

但是各种各样的事情都会干扰这个过程。

根据美国哥伦比亚大学2011年研究人员的一项研究，那些睡眠不足的人每天摄入的热量几乎比那些睡眠充足的人多300卡路里。

这是因为当我们没有足够的睡眠时，饥饿激素会增加，会告诉大脑需要吃更多的东西。

哥伦比亚大学的研究人员指出，睡眠不足的女性在睡眠不足的日子里摄入的脂肪增加了约30克。这是男性平均增加量的四倍。

在2013年的一项研究中，那些得知不久会遇到“艰难时期”的人会比获得中性信息的人吃更多的食物。

一听说“有麻烦了”，人的生存本能就被激发了，对巧克力等高热量零食的渴望也随之增加。

还想再吃一块小饼干？吃就吃吧，开心一点。研究人员发现，当你对某个愉快的体验感到内疚时，内疚本身也会带来快感，进而鼓励你再次去做这件事。

兰卡斯特大学的Cary Cooper说，如果我们认为某件事会带来不守规矩的快感，它会在心理上促进食欲，而这种内疚可能会让你想吃更多。

大脑中的食欲控制区域非常接近情绪控制区域 —— 边缘系统 —— 这就是为什么我们的情绪变化会影响食欲。

智能手机和平板电脑等设备发出的蓝光可能会增进饮食。

今年的研究发现，蓝光下你的食欲会持续增加。

蓝光的照射还会改变人们的新陈代谢。血液测试显示，接受蓝光受试者的胰岛素和葡萄糖水平都更高。

一种可能的解释是，夜间明亮的蓝光会干扰我们的生物钟。而生物钟可以控制我们什么时候觉得需要进食。

(Chinadaily.com.cn)