A new study published in Food Quality and Safety reveals that hunger enhances the immediate liking and physiological arousal triggered by sweetness, irrespective of calorie content. The research, conducted by scientists from Jiangnan University and the University of Oxford, also found that people who regularly consume non-nutritive sweeteners (NNS) show increased activity in the dorsolateral prefrontal cortex (DLPFC), a brain region linked to self-control, when tasting sweet solutions.
Excessive sugar intake is a major driver of obesity, type 2 diabetes, and cardiovascular disease. Non-nutritive sweeteners have been widely adopted as low-calorie alternatives, but concerns persist that chronic use might decouple sweet taste from metabolic energy signaling, potentially reshaping taste preferences and reward pathways. Long-term trials have yielded conflicting results, highlighting the need for deeper investigation into how metabolic state and habitual NNS use jointly influence sweet preference.
The study directly compared habitual sugar consumers and habitual NNS consumers, measuring their responses to sweetness-matched solutions under both hungry and satiated conditions. Using subjective ratings, emotional assessments, electrocardiogram (ECG), and functional near-infrared spectroscopy (fNIRS), the team uncovered a dissociation between self-reported liking and brain/body responses.
Participants consistently rated all sweet solutions as more enjoyable when hungry, regardless of whether they contained sugar or only NNS. This hunger-driven boost was accompanied by physiological signs of sympathetic nervous system arousal, including significantly shortened R-R intervals and increased heart rate. Contrary to the team's initial hypothesis, hunger did not selectively favor caloric sugar over non-caloric sweetness. “The craving for energy made sweetness itself more appealing, not the calories behind it,” the authors noted.
More strikingly, habitual NNS consumers showed a distinct neural signature. While their self-reported liking and emotional responses did not differ from sugar consumers, fNIRS revealed significantly stronger oxygenated hemoglobin responses in the left DLPFC — a key region for cognitive control and dietary self-regulation. This neural difference emerged even though all samples were tasted blindly and matched for sweetness intensity, ruling out simple perceptual explanations. The study's emotion analysis, however, involved a small sample of 15 participants per group, so those findings should be interpreted with caution.
“Hunger seems to turn up the volume on sweetness itself, making it more appealing whether it comes with calories or not,” the authors said. “That was a surprise — we expected hungry people to reach specifically for sugar. But we also saw that habitual NNS users showed a stronger brain response in a region linked to self-control. It is as if their brains are working a little harder to keep their sweet intake in check.”
These findings offer practical guidance for public health and the food industry. Because hunger enhances the appeal of any sweet taste, replacing sugar with NNS in snacks consumed between meals might still satisfy cravings without adding calories. The heightened brain activity in habitual NNS users raises the possibility that these sweeteners could help reinforce cognitive control over food choices, though this remains to be tested. For now, the study suggests that sweetness itself — not just its energy content — powerfully drives hunger-related eating behavior. Reformulating products to be less sweet overall, while ensuring they are still pleasurable, may be a more effective long-term strategy than simply swapping sugar for zero-calorie alternatives.
The research was funded by the National Key Research and Development Program of China and the Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province. The full study is available at https://doi.org/10.1093/fqsafe/fyag046.
