A sweet snack might not stop you from relaxing, but your body may stay more activated than you think.
In a study published in International Journal of Psychophysiology, researchers found that consuming glucose before a relaxation session did not change how relaxed participants felt. But it did affect how their bodies responded behind the scenes.
The study, conducted by researchers at University of Konstanz, included 94 healthy adults who were randomly assigned to drink either a glucose solution or water after fasting. Participants then either received a massage or rested quietly while researchers measured heart activity.
Both groups reported feeling relaxed, and physiological markers tied to the body’s “rest and digest” system increased during relaxation, regardless of what they drank beforehand.
But there was a difference in another part of the nervous system.
Participants who consumed glucose showed continued activity in the sympathetic nervous system, which is responsible for alertness and stress responses, even during relaxation. In contrast, those who drank water showed a clearer shift toward a more fully relaxed state.
In practical terms, that means participants could feel calm while their bodies remained slightly more switched on than expected.
The findings point to a subtle but important distinction between subjective relaxation and physiological state. While relaxation techniques like massage still had clear effects, glucose appeared to keep one part of the body’s stress response system more engaged.
The study has several limitations. It examined a single, short-term exposure to glucose in a controlled setting and included a relatively small group of healthy adults. The results do not address long-term health effects or typical eating patterns.
Researchers also emphasized that both branches of the autonomic nervous system need to be considered together. Looking at only one system, such as the parasympathetic response, could miss important changes happening in parallel.
The study was funded by the Committee of Research (AFF) of the University of Konstanz. Additional support was provided through the Konstanzia Fellowship of the University of Konstanz.