BBC Reel｜为什么明明饱了，还是忍不住想吃东西？

Why do we keep eating when we feel full?

Dr. Christine: Our research at the University of Leeds shows that our overall hunger stems from a drive to eat, and that's determined by our resting metabolic rate, which is the energy that our body expends to sustain our everyday bodily functions and to a lesser extent, by our physical activity levels. But there's also an episodic mechanism. So on a meal-to-meal basis, signals such as an empty stomach, low blood glucose and appetite related hormones can also trigger or signal hunger.

Host: And what about if you feel hungry and then you don't eat and it goes away, even though you haven't responded to that feeling of hunger?

Dr. Christine: So hunger feelings can go away after a while. So during prolonged fasting or any kind of food deprivation situations, our body produces ketone bodies and these have been proposed to suppress appetite. But this is really early days in that area of research.

Hunger is not only influenced by internal factors, but also external factors, and we can forget that we're hungry under some circumstances because we're distracted or that we're busy. Some people love to eat and they're very in tune with their hunger sensation, so it's definitely not a one size fits all kind of common.

(But why do we sometimes still feel like eating even when we're not hungry?)

Dr. Christine: So we have several appetite systems in the brain, and one of them is the hedonic system. Even though we're not hungry, we can still want to eat because we have that pleasure system in the brain, which can override these sensations of fullness, for example. So let's say, for example, we're at a restaurant and we see the dessert menu, but we've just had the big meal and we're full, but we still want that dessert because it's so tasty.

Host: And Charles, can I bring you in at this point? Is this a physical thing or is this really more about psychology?

Prof Charles: Oh, I think definitely a bit of both. Because as a psychologist myself, I'm sort of more interested in those external factors, such as, you know, the smell of appetising food when we wander through a train station or a shopping centre, more often than we realize, it's these external cues, too energy dense. You know, great-smelling food, that suddenly make us think "ah, maybe I will order, eat, drink one of those things". When before having smelled or seen that external kind of food cue, we weren't really thinking about food at all.

We may even have sort of evolved our kind of visual systems to be able to, you know, look at a scene and almost instantaneously decide if there's something edible out there. And if so, what's the most energy dense, highest fat food? And then our brain immediately pays attention to that. And if that food is in movement or in motion, it's even more attractive.

And this is something I think that the food marketers are sort of intuitively picked up on showing those pictures, you know, oozing cheese, coming out of a burger, say, or a slice of pizza or lasagne. And that just becomes something that's a very powerful cue that draws our attention that we can't ignore to, to order or to eat more than we otherwise might.

词汇表
stem from [stem] 起源于，来自
resting metabolic rate [ˈrestɪŋ ˌmetəˈbɒlɪk reɪt] 静息代谢率（人体在静息状态下维持基本生理功能所需的能量消耗）  
episodic [ˌepɪˈsɒdɪk] 偶发的，不定期的
low blood glucose [ˈɡluːkəʊs] 低血糖
appetite related hormones [ˈæpɪtaɪt rɪˈleɪtɪd ˈhɔːməʊnz] 食欲相关激素
prolonged fasting [prəˈlɒŋd ˈfɑːstɪŋ] 长期禁食
food deprivation [ˌdeprɪˈveɪʃn] 食物匮乏，食物剥夺
ketone body [ˈkiːtəʊn] 酮体（在长期饥饿或低碳水饮食时增加，以满足身体对能量的需求）
be in tune with [tjuːn] 与…协调一致，能敏锐感知  
hunger sensation [ˈhʌŋɡə(r) senˈseɪʃn] 饥饿感
one size fits all 一刀切的，通用的
hedonic [hiːˈdɒnɪk] 享乐的，快乐的，享受的
override [ˌəʊvəˈraɪd] 压倒，优先于，凌驾于
sensations of fullness [senˈseɪʃnz əv ˈfʊlnəs] 饱腹感
dessert [dɪˈzɜː(r)t] 餐后甜点，甜食
appetising [ˈæpɪtaɪzɪŋ] 开胃的，诱人的，引起食欲的
wander through [ˈwɒndə(r)] 漫步于，穿梭在
energy dense [ˈenədʒi dens] 高能量密度的（指食物或饮料中含有高热量的能量）
instantaneously [ˌɪnstənˈteɪniəsli] 瞬间地，即刻地
edible [ˈedəbl] 可食用的；食物
intuitively [ɪnˈtjuːɪtɪvli] 直觉地，本能地
pick up on 注意到，意识到，领悟
oozing cheese [ˈuːzɪŋ tʃiːz] 渗出的芝士，流淌的芝士
lasagne [ləˈzænjə] 千层面（一种意大利分层烤面食）

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