I think the parent is referring to this: http://www.bbc.com/news/health-36772303

> Artificial sweeteners can boost appetite by activating hunger pathways in the body, scientists have found in animals.

> In fruit flies and mice, the mismatch between sweet taste and fewer calories sends the body into "feed me" mode, the journal Cell Metabolism reports. But UK nutritionists say this does not mean the same is true in humans.