Well I think I mentioned previously in this thread already that I'm pretty confident they're not carcinogenic, so that's not the question.
However I do hypothesize that they're likely to cause eating issues though. I just see far too often people start guzzling a diet soda and then go grab a bag of chips. It goes together like booze and cigarettes for smokers.
I suppose it is possible that could affect some people that way. However there is no evidence that this is a causal relationship.
A lot of fat people, will try to lose weight by switching to diet, but they still continue their other poor eating habits. So that may also account for.
Then you have to consider that people drinking diet, may be eating an excessive amount of things with sugar alcohols. If you eat enough of that it can affect your blood sugar a little and possibly increase appetite.
So yea, I would agree that aspartame affecting certain people's eating habits is a legitimate hypothesis based on observational evidence. By eliminating sugar alcohols, and having psychologists on hand, you may be able to isolate the variables. It could be made into a proper experiment if done in that manner.