A neuroscientist at the Oregon Research Institute has used MRI scans to conclude that sugar activates the same brain regions that are activated when a person consumers drugs like cocaine. He also found that heavy users of sugar develop tolerance, needing higher doses of sugar to obtain the same effect.
Dr. Avena, a psychologist at Princeton University was able to induce sugar addiction in rats and found that rats with intermittent access to sugar will drink in a binge-like manner that releases Dopamine in the Nucleus Accumbens, (region in the brain) the classic effect of most substances of abuse. She also found that intermittent sugar access acts in a similar manner as opioid addiction.
The research points out the potential of sugar to be an addictive substance, which is especially concerning with the current trend to expose children to high doses of sugar.