夜雨聆风
Imagine you’re in a meeting room when someone brings out the biscuits – a packet of Jammie Dodgers, perhaps, or a nice little plate of custard creams. Maybe you want one and maybe you don’t, but the chances are the people around you are all responding differently: someone will grab a couple straight away, someone else will eat one without seeming to notice, another will barely be aware the biscuits exist, and someone will spend the whole meeting wanting one but not taking it. Our appetites and responses to food vary wildly – but what’s going on behind the scenes to govern them? And has modern food somehow hijacked the process? Grab a biscuit (or don’t) and settle in.
“First, it’s important to distinguish between hunger and appetite,” says Giles Yeo, a professor of molecular neuroendocrinology at the University of Cambridge and the author of Why Calories Don’t Count. “Hunger is a feeling – it’s what happens in the run-up to you deciding you need to eat something. Appetite is everything that surrounds why we eat – including hunger, fullness and reward, or how you actually feel when you eat. Those three sensations all use completely different parts of the brain, but they all work together.”
Hunger is regulated by the hypothalamus, which sits behind the bridge of the nose, at the base of the brain, monitoring your body’s levels of blood sugar and the hormones leptin and ghrelin to check whether you’re in an energy deficit. Fullness is regulated by the hindbrain, located roughly where your skull meets your neck: when your stomach stretches, the vagus nerve sends a signal to this area telling you that you’re physically full. Reward, meanwhile, is regulated by a diffuse network of neurons that sit higher up in the brain, driven by dopamine and its search for pleasurable activities.
“All those parts of the brain speak to each other, which is why if you’re really hungry, food that offers very little ‘reward’ – like rice or bread – can be delicious. Or why you can feel full but still feel ready for chocolate cake, because it’s activating your reward system even though your hindbrain says you’re full,” says Yeo. “It’s like a triangle that changes shape depending on your circumstances, with appetite in the middle.”
So what’s going on with the biscuits? Well, part of the reason we might respond differently to them is how hungry or full we are in the moment, but it’s likely that genetics also play a part. “We all know people who love food, and people who simply see it as fuel,” Yeo continues. “Food-is-fuel people will get hungry eventually, but it happens far closer to the time that they actually need to eat than for others. It’s also likely to be a matter of how much – or how little – food is needed to trigger the brain’s reward response. We know there are more than a thousand genes that influence our appetite, so it’s a very complex system.”
Another element in all this is that scent, sight and even sound cues activate the brain’s appetite circuitry independently of how much energy we have stored, resulting in what neuroscientists call “hedonic” hunger. “When we see food, sensory and olfactory input interacts with brain regions that regulate appetite, and temporarily increase dopamine signalling,” says Timothy Frie, a nutritional neuroscientist. “That heightens our motivation to eat, even if our physiological energy needs have already been met. The sensation of hunger isn’t coming from an empty stomach, but from a conditioned, cue-driven response where the brain and body are preparing for intake based on what you see. Sound can also play a part, with its influence coming primarily through learned associations, like the repeated pairing of a sizzle or a crunch with a desirable taste or sensation.”
One more complication is that all these systems can be confused, or at least disrupted, by stress. “When we’re stressed or experiencing some degree of cognitive overload or fatigue, the regulatory capacity of our prefrontal cortex is reduced, while appetite and reward systems remain active,” says Frie. “The brain’s demand for a rapid and reliable source of fuel also increases in response to stress. That creates a predictable imbalance: stronger drive to eat with reduced ability to regulate that drive.” Sugary, salty, fatty and especially ultra-processed foods rapidly increase glucose availability and light up motivation pathways in the brain, and when we’re stressed, the brain assigns higher priority to these foods because they provide quick and efficient energy.
Appetite can also be disrupted over time. When we overeat refined carbs, sugars and fats frequently over a long period, our receptors for insulin and leptin (which regulates energy balance and appetite) can become muted, reducing their responsiveness and making it harder for us to tell when we should stop eating.
Food companies, of course, know all this, and often respond to it by hijacking the systems that lead us astray: pumping delicious scents through the air in fast-food restaurants, say, or designing foods that pair hyperpalatability with sensory cues like a satisfying crunch. To make matters worse, although our in-built satiety systems are fairly good at roughly judging the energy content of foods that are mostly fat or protein, they’re terrible at estimating it in foods that mix refined carbs and fat, making it easy to enormously overeat things like biscuits, pastries and pizza.
Where does this leave us? Unfortunately, in a situation where our basic drives and biological mechanisms haven’t changed much since our hunter-gatherer past, but are being exploited by the endless food options available. “Many of us live in a supernormal, overstimulating and engineered food environment,” says Frie. “Our brains are saturated with cues to eat, but they aren’t necessarily equipped to respond to so many cues for a long period of time. The best thing we can do for ourselves is to develop what I call food-mind fluency: the ability to recognise what is driving the urge to eat in that moment and respond with awareness and conscious intention.”
This allows us to regulate and manage the sequence of events that occur between a food cue and a food response. In practice, Frie says: “That could mean inserting a brief pause before acting on the impulse to eat and asking a single question: ‘What is generating this signal right now: energy need, stress, habit or exposure to a cue?’ That step engages our prefrontal cortex, which allows us to shift our behaviour from automatic to intentional.”
But when the vast majority of non-infectious diseases we face as a species are diet-related, preaching personal responsibility probably isn’t enough. “Personal responsibility is fine and we need to talk about it and give people advice,” says Yeo. “But I also think it absolves policymakers and government from the public health decisions they need to take in order to try to improve our food environment. It has to be a holistic thing.”
词汇
appetite /ˈæpətaɪt/n. 食欲；欲望
例句：Stress often increases people’s appetite for junk food.
hijack /ˈhaɪdʒæk/v. 操控；劫持
例句：Modern processed food hijacks human natural appetite mechanisms.
distinguish /dɪˈstɪŋɡwɪʃ/v. 区分；辨别
例句：It’s vital to distinguish real hunger from emotional appetite.
molecular /məˈlekjələ(r)/adj. 分子的
例句：He majors in molecular neuroendocrinology research.
neuroendocrinology /ˌnjʊərəʊˌendəʊkrɪˈnɒlədʒi/n. 神经内分泌学
例句：The professor’s research focuses on neuroendocrinology related to eating.
hypothalamus /ˌhaɪpəˈθæləməs/n. 下丘脑
例句：The hypothalamus controls human hunger regulation.
hormone /ˈhɔːməʊn/n. 激素
例句：Leptin and ghrelin are key hormones controlling hunger.
deficit /ˈdefɪsɪt/n. 不足；缺口（能量亏空）
例句：Energy deficit will trigger the feeling of hunger.
hindbrain /ˈhaɪndreɪn/n. 后脑
例句：The hindbrain receives fullness signals from the vagus nerve.
vagus /ˈveɪɡəs/adj. 迷走的
例句：The vagus nerve connects stomach and brain.
diffuse /dɪˈfjuːz/adj. 弥散的；分散的
例句：Reward-related neurons form a diffuse brain network.
neuron /ˈnjʊərɒn/n. 神经元
例句：Dopamine works among countless brain neurons.
dopamine /ˈdəʊpəmiːn/n. 多巴胺
例句：Delicious food raises dopamine levels in the brain.
genetics /dʒəˈnetɪks/n. 遗传学；遗传因素
例句：Genetics greatly affect individual appetite differences.
scent /sent/n. 气味；香味
例句：The scent of bread easily arouses hedonic hunger.
olfactory /ɒlˈfæktəri/adj. 嗅觉的
例句：Olfactory signals can stimulate appetite instantly.
cue /kjuː/n. 提示信号；诱因
例句：Food visuals act as strong appetite cues.
hedonic /hiːˈdɒnɪk/adj. 享乐性的
例句：Hedonic hunger arises from sensory stimulation not physical need.
conditioned /kənˈdɪʃnd/adj. 条件反射的
例句：Conditioned responses make you crave food at familiar smells.
sizzle /ˈsɪzl/n. 滋滋声
例句：The sizzle of frying meat triggers appetite.
prefrontal cortex /ˌpriːˈfrʌntl ˈkɔːteks/n. 前额皮质
例句：Prefrontal cortex helps control impulsive eating.
fatigue /fəˈtiːɡ/n. 疲惫
例句：Mental fatigue weakens appetite control ability.
glucose /ˈɡluːkəʊz/n. 葡萄糖
例句：Sweets quickly boost blood glucose levels.
refined /rɪˈfaɪnd/adj. 精制的
例句：Refined carbs harm the body’s satiety regulation system.
insulin /ˈɪnsjəlɪn/n. 胰岛素
例句：Long-term overeating blunts insulin sensitivity.
receptor /rɪˈseptə(r)/n. 受体
例句：Hormone receptors become less sensitive after overeating.
muted /ˈmjuːtɪd/adj. 变迟钝的；弱化的
例句：Overeating makes leptin receptors muted.
hyperpalatability /ˌhaɪpəˌpælətəˈbɪləti/n. 超高适口性
例句：Junk food is designed for hyperpalatability.
satiety /səˈtaɪəti/n. 饱腹感
例句：Our satiety system struggles with refined carb-fat mixes.
hunter-gatherer /ˈhʌntə ɡæðərə/n. 狩猎采集者
例句：Human appetite evolved in hunter-gatherer environments.
supernormal /ˌsuːpəˈnɔːml/adj. 超常态的
例句：Modern food environment is supernormal for human brains.
fluency /ˈfluːənsi/n. 通透认知；熟练把控
例句：Food-mind fluency helps avoid mindless eating.
impulse /ˈɪmpʌls/n. 冲动
例句：Pause before giving in to eating impulse.
absolve /əbˈzɒlv/v. 免除（责任）
例句：We cannot absolve governments of food regulation duties.
holistic /həˈlɪstɪk/adj. 整体的；全盘的
例句：Improving food environment needs holistic measures.
高频短语
behind the scenes 在背后；内在机理
in the run-up to 在…… 前夕 / 之前
cognitive overload 认知过载
light up pathways 激活神经通路
refined carbs 精制碳水
in-built satiety systems 天生饱腹调节系统
insert a brief pause 短暂停顿
shift from automatic to intentional 从本能转向理性
diet-related diseases 饮食相关疾病
句型
句型 1 Imagine..., but the chances are...想象……，但大概率人们反应各不相同（举例引入现象）
例句：Imagine snacks appearing on desk, but the chances are people react differently.
句型 2 A is regulated by..., while B is controlled by...
A 由…… 管控，而 B 由…… 调控（分点介绍生理机制）
句型 3 ...result in..., even if...
即便……，仍会导致……（诱因带来额外食欲）
句型 4 When..., the capacity of... is reduced while... stays active
当…… 时调控能力下降，但另一系统仍活跃（压力影响食欲模板）
句型 5 Personal responsibility isn’t enough; we also need...
个人自律不够，还需要宏观举措（辩证结尾）
长难句
长难句 1Hunger is a feeling – it’s what happens in the run-up to you deciding you need something to eat. Appetite is everything that surrounds why we eat – including hunger, fullness and reward.
结构破折号解释概念，并列分句
译文：饥饿是一种生理感受，是身体发出缺食信号；而食欲包含所有促使人进食的因素：饥饿、饱腹、愉悦奖赏。
长难句 2When we see food, sensory and olfactory input interacts with brain regions that regulate appetite and temporarily increase dopamine signalling.
结构时间状语 + 主句 + 定语从句
译文：看到食物时，视觉、嗅觉信号和控食欲脑区发生交互，短暂提升多巴胺分泌。
长难句3 When we’re stressed or experiencing fatigue, the regulatory capacity of our prefrontal cortex is reduced while appetite and reward systems remain active.
结构when 从句 + while 对比并列
译文：人处于压力或疲惫时，前额皮质自控能力下降，但食欲和奖赏系统依旧活跃。
长难句 4Although our in-built satiety systems are fairly good at judging fat or protein, they’re terrible at estimating mixed refined-carb-and-fat foods.
结构 although 让步从句
译文：人体先天饱腹机制擅长判断油脂、蛋白质热量，却很难估算精制碳水 + 混合型食物的热量。
长难句 5 Our basic biological drives haven’t changed much since hunter-gatherer times but are constantly exploited by modern engineered food environment.
结构并列转折
译文：人类原始进食本能自狩猎时代变化极小，却不断被精心设计的现代食品环境利用。
长难句 6 That could mean inserting a brief pause before acting on the impulse to eat and asking what triggers the current eating urge.
结构宾语 + 并列动名词
译文：实操方法：想吃前短暂停顿，自问当下想吃是缺能量、压力还是感官诱惑。
