Can Sugar Disrupt Relaxation? A New Study Suggests It Might

Treating ourselves has become almost synonymous with rest and self-care. A post-dinner dessert, a mid-afternoon sweet treat, even that vanilla latte in the morning. These small indulgences have started to feel like part of the ritual of slowing down, almost like a signal to the body that it’s time to relax and reset.

But what if that signal isn’t working the way we assume it is?

What you eat in those moments doesn’t just affect your mood or your taste buds. It also affects systems in the body that control how you shift between stress and rest, known as the autonomic nervous system.

And a new study1 suggests that sugar may influence how easily the body makes that shift into a true state of relaxation.

Sugar & the relaxation response

To understand how sugar interacts with relaxation, the researchers designed a controlled experiment with 94 healthy young adults. Participants were randomly assigned to drink either a glucose solution or water. After that, they went through two different conditions: a standardized massage or a simple resting period. Both are known to help the body downshift into a calmer state.

While this was happening, researchers tracked multiple markers of nervous system activity using heart measurements that reflect two key branches of the autonomic nervous system: the parasympathetic system, which supports rest and recovery, and the sympathetic system, which is more closely tied to alertness and activation.

They also measured subjective feelings of relaxation and then followed participants into a sustained attention task to see whether any physiological changes carried over into performance.

They weren’t just asking “Did people feel relaxed?” They were looking at whether the body actually entered a relaxed state, and whether sugar changed that response.

What changed in the body after sugar intake

Both massage and rest did what they were supposed to do. Participants felt calmer, and their parasympathetic nervous system, the part linked to relaxation, increased activity as expected. From a subjective standpoint, people reported feeling more at ease.

But sugar told a slightly different story under the surface.

After consuming glucose, the sympathetic nervous system stayed more active, even during the massage. This means the body remained in a more alert, activated state instead of fully shifting into deep physiological rest.

Importantly, this didn’t change how relaxed people said they felt. The experience of calm was still there. But the body remained more physiologically alert, even during relaxation.

The researchers also didn’t find evidence that sugar changed the parasympathetic response itself. Instead, it seemed to keep the body in a slightly more activated baseline state during moments that would normally support deeper recovery.

Interestingly, higher blood glucose levels were also linked to slightly better performance on a later attention task. This suggests that the same physiological pattern that kept the body more alert during relaxation may also support short-term focus and performance, even if it slightly blunts full physical relaxation.

The truth about sugar & relaxation 

This study doesn’t suggest that sugar cancels out relaxation or that one sweet treat will derail your nervous system. The effects were subtle and context-dependent, observed in a controlled setting.

But it does highlight something most of us rarely consider. Feeling relaxed and being physiologically relaxed are not always the same thing.

Your body can register calm while still holding onto a low level of activation in the background. And according to this research, sugar may be one of the factors that nudges the system in that direction, especially when you’re trying to wind down.

It also adds nuance to how we think about “treating ourselves” in the name of rest. A sweet snack during downtime might feel like part of the relaxation process, but biologically, it could be keeping the body slightly more alert than we realize.

The takeaway

This study points to a simple idea that metabolic inputs and nervous system states are deeply connected. What we eat can subtly shape how easily we shift between activation and recovery.

For most people, this isn’t about cutting out sugar in moments of rest altogether. It’s about awareness. Noticing that the body’s ability to fully relax can be influenced by more than breathwork, environment, or mindset alone.