Scientists have long known that the gut sends signals to the brain about how much energy we’ve consumed, but a new study shows that the brain isn’t just counting calories. It can actually tell what kind of nutrient you’ve eaten, and it has a special pathway just for recognizing glucose.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have uncovered a gut-brain circuit that allows the brain to distinguish glucose from other nutrients like fats or amino acids. The findings, published in Neuron, help explain why sugar cravings can feel so powerful and why not all calories affect us the same way.
Using a mix of advanced neuroscience tools, the researchers showed that when glucose enters the small intestine, it sends a signal to a specific group of neurons in the brain’s hypothalamus. These neurons, known as CRF neurons, are part of the body’s stress and energy regulation systems and respond rapidly and selectively to real glucose, but not to calorie-free sweeteners or other nutrients.
When researchers blocked the activity of these neurons in mice, the animals stopped preferring glucose over other nutrients, suggesting this circuit is essential to sugar-specific appetite.
In short: the brain knows when it’s getting sugar, and it reacts differently than it does to other forms of energy.
That discovery has big implications for metabolic health. If the brain is wired to favor glucose, it could help explain why sugar feels more satisfying, or more addictive, than other foods. It may also shed light on why some artificial sweeteners don’t curb cravings: they might not activate this pathway at all.
“This research opens up new therapeutic possibilities for metabolic diseases,” said study leader Professor Greg Suh in the KAIST release. “Moving forward, we aim to investigate how similar circuits detect other essential nutrients, such as amino acids and fats, and how these systems interact.”
The findings could lead to new strategies for managing obesity and diabetes, not just by controlling calories, but by modulating how the brain interprets what we eat.
The research was supported by the Samsung Science & Technology Foundation, the National Research Foundation of Korea, the POSCO Cheongam Science Fellowship, the Asan Foundation Biomedical Science Scholarship, the Institute for Basic Science and the KAIST KAIX program.