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There are scientific reasons why you may be too full for more food but still crave a treat.
This is a common experience, especially during the holidays. You’ve already eaten and overeaten. You start to feel like you might really have a problem if you don’t stop, and then someone brings out dessert.
Suddenly, you discover that there’s actually a little room left in your stomach for sweets. It turns out there are scientific reasons why you may be too full for more food but still crave a treat.
Your brain and stomach agree that there really is room for dessert
Your stomach is extremely adaptable and changes shape as you eat and digest food. When you eat, the smooth muscles in your stomach relax, allowing the stomach to expand, but only to a certain extent. The average stomach expands to between 1 and 1.5 liters (34 to 50 ounces), but this varies from person to person. A full stomach can expand to four liters or 135 ounces.
Heavy foods such as proteins and fats break down slowly in the stomach and make you feel bloated for longer. At the same time, carbohydrates and sugar are absorbed relatively quickly. So even when your stomach is full, soft and light desserts don’t make much difference. Of course, stomach expansion is not directly related to feeling full, but overeating can cause discomfort.
Hormones are what really control when you feel hungry or full. The feeling of hunger comes from a hormone called ghrelin. It is produced by the stomach and sent to the hypothalamus. The higher your ghrelin levels, the hungrier you become. Typically, ghrelin production increases before eating and decreases after eating. Ghrelin is the main culprit for hunger, but it is not the only hormone that influences it.
Eating dessert activates the reward centers in the brain, overrides the feeling of fullness, and increases your desire to eat. In a 2025 study published in the journal Science, scientists worked with mice to discover the reason for the desire for dessert.
The mice were given regular rat food for 90 minutes, followed by a 30-minute dessert period. During the meal, the mice ate until they were full. If they were offered more mouse food during the dessert period, they nibbled on it but ate only a little more. If they were given a sugar-rich mixture, they pounced on it. Researchers trace the behavior to a group of neurons in the hypothalamus called POMC neurons.
These neurons are responsible for telling your brain that you are full, but they do something strange in the presence of sweets. When eating dessert, POMC neurons release beta-endorphin, a naturally occurring opioid that triggers feelings of pleasure and reward. When researchers blocked the associated opioid pathway, the mice left their dessert untouched.
This so-called hedonic hunger may seem more psychological than physical, but it is just as real. So the next time you’ve overeaten but crave ice cream, now you know why. | BGNES
