I don't think it would make much of a difference, to tell you the truth. I'm sure for some people... but like for me, when I was a kid, we didn't have McDonalds very much. And when we did go, while (don't get me wrong) I did like toys, I also liked, oh, I dunno.... the food! The greasy, salty, heavenly food. I didn't need the toy to get me to come back, I liked the food. I mean I'm sure some kids like the toy, but the toy wasn't the reason we went.
And I'm not some obese person either (no offense to anyone who is). I can eat McDonalds every so often without tipping the scales. I think it should be up to the parents how often kids eat at McDonalds, and no amount of bugging from the kids should persuade the parents otherwise. However, that would require parents to step up, and, oh, I dunno, actually parent. So that may be asking too much.