What Contributes to Appetite?

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People lost interest in a food after eating to fullness; brain responses to pictures of that food didn't fade.

Food cues may keep triggering learned reward signals even when hunger has already been satisfied.

Overeating may begin not with an empty stomach but with a brain that still reacts to the sight of food.

You finish a meal, feel completely full, and then someone opens a box of pastries. A moment ago, your body seemed finished with food. Now, suddenly, dessert sounds possible.

We usually think of hunger as the thing that drives eating. In one sense, that’s true. The body has a remarkably sophisticated system for regulating energy balance. When we need food, signals rise. When we have had enough, signals should help quiet the urge to eat. But modern life surrounds us with something that biology did not quite prepare us for: a constant stream of food cues. Packaging. Ads. Bakery windows. Delivery photos. The glow of a refrigerator at midnight.

A recent study in Appetite studied why we may not be able to avoid overeating when faced with these food cues. When we are full, the brain does not stop treating these cues as rewarding. Even after people had eaten enough of a food to reduce its appeal, their early brain responses to images of that food stayed largely unchanged. Part of the brain may keep saying “more” even after the body has already said, “That’s enough.”

When Fullness Does Not End the Want

Ninety university students rated a set of foods while they were hungry, and two similarly appealing foods were selected for each person. Halfway through the experiment, participants were fed one of those foods until they no longer wanted more of it. That food became the “devalued” one, meaning it should have lost much of its motivational pull.

So far, this sounds like common sense. If you eat enough potato chips, the chips should become less tempting. If you eat enough brownies, brownies should lose some of their magic. The study confirmed that people themselves reported experiencing this. After the meal, people rated the sated food as less desirable. Their behavior in the task also shifted in the expected direction, suggesting they knew, on some level, that the food no longer held the same value.

While the students completed a reinforcement learning task, rapid electrical activity responses were recorded from the scalp. They focused especially on a signal called reward positivity, an event-related potential often linked to the brain’s early evaluation of better-than-worse outcomes. The key question was whether this signal would shrink when participants saw images of the food they had just eaten to satiety. It did not: The brain continues telling you to keep eating even after you recognize that you’re full.

Before the meal, food images produced a clear reward-related brain response. After the meal, that early neural response still appeared, even for the food people had just stuffed themselves with. In other words, the participants’ choices and ratings showed devaluation, but the early brain signal did not. The mind can “know” that a food is no longer worth pursuing, but a fast and automatic part of the brain still reacts to its cue as though it carries reward.

This study helps explain one of the most frustrating aspects of eating. Overeating is not always a simple failure of willpower. It may begin earlier than that, in the split second when a cue grabs the brain before deliberate control has had time to catch up.

A food cue is not the food itself. It can be a picture, a smell, a crinkling wrapper, a logo, a familiar box on the counter. Yet through repetition, these cues become powerful. They come to stand in for the reward they predict. In the language of psychology, they become learned signals. In ordinary life, they become temptations that seem to win out over reason.

What Contributes to Appetite?

Take our Emotional Eating Test

Find a therapist near me

In the study, the participants were not oblivious to their overeating. Their ratings changed, as did their performance. Part of the brain, or perhaps part of the mind, clearly registered that the sated food was now less valuable. What remained stubborn was the early neural response to the cue. This suggests that self-control may not begin by erasing temptation, but by overriding it. The first wave of evaluation may still arrive, but later processes can still step in and say no. Seen this way, restraint is not the absence of desire. It is the ability to outlast a signal that the brain continues to generate.

A More Crowded Food World

Our ancestors did not live among delivery apps, convenience-store aisles, and high-resolution food photography engineered to hold attention. Today, many people move through environments saturated with cues that were designed to be noticed and remembered. The study’s central insight is that these cues may retain some of their punch even after our biological need has been met.

A picture of food can carry traces of past rewards. It can awaken old associations even when the stomach is full. And if that is true, then overeating is not simply about hunger overwhelming reason. Sometimes it may be the opposite: Reason understands that the value is gone, while an older, faster system continues to light up anyway. The modern challenge, then, is not just learning when to eat, but learning how to live among cues that keep signaling reward even when the body no longer wants it.

Sambrook, T. D., Wills, A. J., Hardwick, B., & Goslin, J. (2025). Devaluation insensitivity of event related potentials associated with food cues. Appetite, 108390.

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