Sugar is not a harmless substance but actively changes the brain with repeated exposure (that is, eating sugar regularly). Here's a few links from various venues which discuss the neurobiological effects of sugar:

https://onlinelibrary.wiley.com/doi/full/10.1002/brb3.70338

https://www.texasinstituteforneurologicaldisorders.com/uncat...

https://www.healthline.com/health/food-nutrition/experts-is-...

https://www.inverse.com/mind-body/heres-what-happens-to-your...

I'll even throw in an AI-generated answer from the less-than-eloquent prompt "sugar addiction brain":

> Sugar addiction triggers neurobiological changes in the brain’s mesolimbic dopamine pathway, specifically affecting the nucleus accumbens and prefrontal cortex. Consuming sugar causes a surge in dopamine and endorphins, creating a pleasurable "high" that reinforces consumption. Over time, this repeated stimulation leads to neuroadaptation, characterized by:

> Downregulation of D2 receptors: The brain reduces its dopamine receptors, requiring more sugar to achieve the same effect (tolerance).

> Altered gene expression: Changes in receptor availability in the midbrain and frontal cortex.

> Hippocampal damage: High sugar intake can reduce new neuron production, impairing memory and learning.

>These mechanisms drive compulsive intake, cravings, and withdrawal-like symptoms (such as anxiety and irritability) when sugar is removed. While not formally classified as a substance use disorder in humans, the behavioral and neurochemical parallels to drug addiction (such as bingeing and loss of control) are well-documented in preclinical models and supported by human neuroimaging studies.