Key points
A team uncovered a brain circuit that may explain why we crave a sweet treat when we are already full.
Sugar activates receptors in the brain that opioid drugs also target, making dessert difficult to resist.
Rather than relying on sheer willpower, understanding brain biology may help you manage your sugar cravings.
----
For many of us, dessert is not just a treat; it is a ritual. A scoop of ice cream on a warm cookie or a forkful of chocolate cake satisfies a craving deeper than hunger. A recent discovery from Germany may explain why we reach for dessert even after we are already full. The team uncovered a neural circuit in the brain that overrides your body’s satiety signals and fuels your sugar cravings. By tapping into the same receptors that opioid drugs target, it is no wonder that dessert can be so difficult to resist.
Hunger vs. Cravings
Hunger is your body’s way of telling you to eat. Low blood sugar, nutrients, and energy levels trigger the release of hormones like ghrelin and other chemical messengers that enable the gut and brain to communicate. This gut-brain connection is how we know it is time to eat.
Food cravings, on the other hand, often have little to do with hunger. When you start dreaming of rich chocolate cake or your favorite salty chips, your body may not actually be hungry. Cravings are rooted in the brain. Emotions, stress, or sensory stimuli such as smells and sights can trigger them. Our cravings are also shaped by our habits. The more you indulge in a particular food, the harder it becomes to resist.
When you're hungry, almost anything sounds delicious. When you crave a specific food, like chocolate, nothing else will suffice. This is because the brain’s reward system drives our cravings. Regions like the hippocampus and prefrontal cortex, which are involved in memory, pleasure, and motivation, release dopamine neurotransmitters to reinforce the good feelings associated with eating certain foods. Foods high in salt, fat, and sugar are the biggest culprits.
Why Do We Crave Sugar?
Sugar is the body’s quickest source of energy. Natural sugars, such as those found in fruits, milk, and foods containing table sugar, increase blood glucose levels, which can be broken down for energy. This temporary energy boost triggers a surge of dopamine in the brain. People often crave sugar when they are stressed, anxious, or sad because it also provides a temporary mood boost.
Unlike foods high in salt or fat, the sugar craving seems to become more powerful when you are already full. It feels natural to end every meal with dessert. Our innate craving for a sweet treat may have more to do with neurobiology than habit or tradition. This study, published in Science, found that even mice will indulge in dessert.
After fasting overnight, the mice in this study were fed a basic chow meal. They were given 90 minutes to eat until they were full. Once they stopped eating, the team offered each mouse a sugary treat. Given the choice between more chow or sweet treats, the mice consumed nearly six times more calories in sugar.
While the mice ate, the team used fiber photometry to track neuron activity in their brains. What they uncovered was a neural circuit beginning in the hypothalamus, a deep midbrain region that regulates satiety, and extending to reward centers involved in pleasure and motivation. Neurons in the hypothalamus activate when the animal is full, releasing a chemical called alpha-melanocyte-stimulating hormone. This hormone reduces appetite and helps the animal stop eating.
Introducing sugar seems to trigger the opposite effect. The smell or sight of sugary food stimulates the release of another hormone called ꞵ-endrophrin. This hormone binds to opioid receptors in reward regions of the brain and blocks satiety signals. Rather than increasing overall hunger, it enhances the animal’s appetite for sugar. Fat-rich food also activated this circuit, but not to the extent of sugar.
Controlling Sugar Cravings
The team discovered that they could influence the mice’s eating behavior using optogenetics, a technique that turns specific genes and neurons “on” and “off.” Silencing neurons in the sugar-reward circuit reduced the animals’ appetite for sugary treats. In another experiment, the mice had the choice between cherry- and lemon-flavored treats made with artificial sweeteners. The team was able to influence which flavor the animals preferred by enhancing this circuit in response to one treat over the other.
This sugar-reward circuit also exists in humans. Brain imaging shows that eating something sweet after a full meal activates similar areas of the human brain. We likely have a similar brain mechanism that processes sugar rewards. Understanding how this circuit works may be the key to controlling pervasive sugar cravings.
Resisting high-calorie, sugary foods has less to do with willpower and more to do with how our brains are wired. Balancing each meal with protein, fiber, and healthy fats can help stabilize blood sugar levels and reduce the brain’s desire for sugar. The next time you feel that sweet tooth kicking in, try reaching for a balanced, nutrient-dense snack that may help curb those sugar cravings before they take over.
References
Minère, M., Wilhelms, H., Kuzmanovic, B., Lundh, S., Fusca, D., Claßen, A., ... & Fenselau, H. (2025). Thalamic opioids from POMC satiety neurons switch on sugar appetite. Science, 387(6735), 750–758.
Dr. W. Hasseltine
