Researchers Discover Why Fructose Fails to Suppress Hunger Like Glucose

Fructose and glucose may contain the same number of calories, but they communicate with the brain through different biological pathways, according to a study published in Neuron. The findings suggest that the type of sugar consumed-not just its calorie content-may influence hunger, food preferences, and eating behavior.

Researchers at the Monell Chemical Senses Center investigated how the two sugars affect brain activity in mice. They found that fructose and glucose send distinct signals from the gut to the brain, producing different effects on neurons that regulate appetite.

Fructose increased levels of the gut hormone peptide YY (PYY), which transmitted signals through the vagus nerve and modestly reduced the activity of agouti-related protein (AgRP) neurons, brain cells known to stimulate hunger. When researchers blocked this signaling pathway, fructose no longer influenced these hunger-related neurons.

Glucose, however, followed a different route. Rather than relying on the PYY-vagus nerve pathway, it produced a much stronger suppression of AgRP neuron activity, suggesting it has a greater impact on reducing hunger signals.

Although both sugars had similar short-term effects on food intake, the mice gradually developed food preferences that reflected the different levels of AgRP neuron suppression. The researchers also tested a sweetener containing both fructose and glucose. This mixture reduced hunger-neuron activity more than fructose alone, and the mice showed a stronger preference for it.

The findings challenge the long-standing belief that hunger-regulating neurons respond primarily to the number of calories consumed. Instead, the results suggest that the brain can distinguish between different types of sugars and process them through separate gut-brain communication pathways.

While the research was conducted in mice, the authors say the findings improve understanding of how different dietary sugars influence appetite and food preferences and may help explain why some sweetened foods and beverages are particularly appealing.

REFERENCE: Aaron D. McKnight, Alan de Araujo, Fang-Yu Hsu, Alexandra G. Vargas-Elvira, Alisha A. Acosta, Miliani M. Smith, Wisdom Iwueze, Guillaume de Lartigue, Amber L. Alhadeff. Attenuated hypothalamic response to fructose via a dedicated gut-brain pathway. Neuron, 2026; DOI: 10.1016/j.neuron.2026.05.013