Anyone can go do an internet search of the two words "aspartame obesity" and come up with a large number of articles that purport that aspartame and related compounds, like monosodium glutamate, cause obesity because they are "excitotoxins", that is, they either kill brain cells or interfere with the appetite supression activity of serotonin in the brain.
Now my impression is that that the doses people are getting are low enough that toxic levels are not being achieved. On the other hand, I decided long ago, not to take any risk and avoid these sorts of products to the extent that I can.
I am curious as to what some of the voracious internet readers like Dru think about the whole issue.