I hate to agree with the International Sweetener's Association, though we both have obvious conflicts of interest (because I enjoy a bit of artificial sweetener with my cocoa, and the odd diet coke).

Artificial sweeteners are often part of a restrained eating pattern. There are studies showing that a restricted diet can lead to an increase in central obesity during catch up growth or weight regain. I think it's also possible that simply having a sweet tooth can be symptomatic of other underlying metabolic issues. I seem to enjoy sweeteners more if I eat more ketogenically--in the sense that it takes less of them to satisfy me
.