What really controls our appetite – hunger, stress or habit?
By The Guardian, April 21, 2026Knowing the difference between hunger and appetite, and understanding the sensory cues behind them, can help us make better decisions about what we eat.
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.”
What is hunger regulated by?
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 increases 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.