The irresistible scent of baking wafting from a high street café, the vibrant colours of a confectionery aisle, the satisfying crunch of a crisp—these aren’t just incidental details of modern life. They are deliberate stimuli in an environment engineered to exploit our most ancient biological wiring, leading us to consume far beyond what our bodies need. The result is a public health crisis where, as experts note, the vast majority of non-infectious diseases we face are diet-related.
The Internal Triangle: Hunger, Fullness, and Reward
To understand how this hijacking occurs, we must first distinguish between hunger and appetite. “Hunger is a feeling – it’s what happens in the run-up to you deciding you need to eat something,” explains Professor Giles Yeo, a molecular neuroendocrinology professor at the University of Cambridge. “Appetite is everything that surrounds why we eat – including hunger, fullness and reward.”
These three sensations form a constantly shifting triangle of influence. Physiological hunger is regulated by the hypothalamus, a region at the base of the brain that monitors blood sugar and hormones like leptin and ghrelin to check for an energy deficit. Fullness, or satiety, is governed by the hindbrain, which receives signals via the vagus nerve when the stomach stretches. Reward, however, is a different system altogether—a diffuse network of neurons driven by dopamine in search of pleasure.
“All those parts of the brain speak to each other,” says Professor Yeo. “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.” Our individual place on this spectrum is partly genetic; over a thousand genes influence appetite, dictating why some people see food primarily as fuel and others are highly motivated by its reward value.
When Cues Override Need: The Power of Hedonic Hunger
This is where our modern world intervenes with profound effect. Neuroscientists identify a powerful phenomenon known as “hedonic hunger” – the drive to eat for pleasure, completely independent of physical need. It is triggered not by an empty stomach, but by sensory cues.
“When we see food, sensory and olfactory input interacts with brain regions that regulate appetite, and temporarily increase dopamine signalling,” explains nutritional neuroscientist Timothy Frie. “That heightens our motivation to eat, even if our physiological energy needs have already been met.” The sight of a glossy doughnut, the smell of fried food, or even the sound of a packet crisping open can activate this circuitry, priming the brain and body for intake. Research pinpoints areas like the nucleus accumbens as a “hedonic hotspot” that amplifies this drive for palatable food.
The food industry has become expert at weaponising this science. Foods are engineered to be hyper-palatable, using precise ratios of salt, sugar, and fat to maximise appeal and override natural satiety signals. Artificial intelligence is now employed to optimise flavours and textures to ensure repeat consumption. Furthermore, our biology is poorly equipped to judge the energy content of foods that mix refined carbs and fats—like biscuits, pastries, and pizza—making overconsumption effortless.
This system is further destabilised 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, seeking a rapid energy source, assigns higher priority to sugary, salty, and fatty foods. Over time, frequent overconsumption can mute our insulin and leptin receptors, a form of desensitisation that makes it harder to feel full, akin to mechanisms seen in substance use disorders.
From Personal Awareness to Public Policy
Faced with this “supernormal, overstimulating and engineered food environment,” as Frie describes it, what can be done? On an individual level, he advocates developing “food-mind fluency”: the conscious ability to recognise the driver behind an urge to eat. “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?’” This simple act engages the prefrontal cortex, shifting behaviour from automatic to intentional.
However, experts argue that relying solely on personal responsibility is inadequate. “It absolves policymakers and government from the public health decisions they need to take,” Professor Yeo states. The UK’s food environment presents significant challenges, with ultra-processed foods (UPFs) constituting over half of the average energy intake and linked to obesity, cardiovascular disease, and mental health issues.
While policies like the Soft Drinks Industry Levy have been implemented, regulation lags behind the science. The British Medical Association is calling for stronger government action, including effective regulation and increased industry accountability. The Health Foundation advocates for population-level, “low-agency” policies such as advertising bans and taxes, similar to tobacco control. A significant gap remains: current UK regulations focus on nutrients like fat, salt, and sugar, often overlooking the harmful effects of the industrial processing itself, leaving many ultra-processed staples unchecked.
The science of appetite, illuminated by work like Professor Yeo’s mapping of over 450 cell types in the human hypothalamus, has never been clearer. The conclusion drawn by public health bodies is that without systemic change to reshape the food environment, our ancient brains will remain locked in a losing battle with modern temptation.