I read that. It's one of the worse Wikipedia pages I've come across. Did you see that it cites the same paper twice, with different style for each one?

Anyway, I read the paper. It concludes "we suggest that sugar, as common as it is, nonetheless meets the criteria for a substance of abuse and may be “addictive” for some individuals when consumed in a “binge-like” manner. This conclusion is reinforced by the changes in limbic system neurochemistry that are similar for the drugs and for sugar. The effects we observe are smaller in magnitude than those produced by drug of abuse such as cocaine or morphine; however, the fact that these behaviors and neurochemical changes can be elicited with a natural reinforcer is interesting. _It is not clear from this animal model if intermittent sugar access can result in neglect of social activities as required by the definition of dependency in the DSM-IV-TR_ (American Psychiatric Association, 2000). Nor is it known whether rats will continue to self-administer sugar despite physical obstacles, such as enduring pain to obtain sugar, as some rats do for cocaine (Deroche-Gamonet et al., 2004). Nonetheless, the extensive series of experiments revealing similarities between sugar-induced and drug-induced behavior and neurochemistry, as chronicled in Sections 4 and 5, lends credence to the concept of “sugar addiction”, gives precision to its definition, and provides a testable model."

As you can see (assuming my HN markup-foo is strong), sugar has not been shown to (or shown not to) lead to the definition of "dependency" for humans, which is a neglect of social activities. So this remains a conjecture with some supporting evidence, but not enough to make the statement that sugar is or even can be an addictive substance.

(Sorry. It is enough to say that it "can be" an addictive substance. Too late to edit.)