In those exact words no, but if you break down the nutritional content of the Sausage McMuffin, yes, probably. A lot of studies are done on rats where even the rats eating "quality" food in the study are still eating things much lower in quality than a fast food muffin. That doesn't even sound particularly challenging.

To be honest, if you're trying to make my point sound absurd by exaggeration, you've shot way too low. The mainstream nutritional view would be that a Sausage McMuffin every morning on its own isn't going to be a particularly bad thing. You need to be a lot more specific with an overall diet to be a problem. You should have asked something like whether you could find a study about eating nothing but lard is available.

To which my reply would be that the principle of charity would make it clear that in general I meant any semi-realistic nutritional view is available, not that there are studies that prove humans can be healthy on a diet of rocks and asbestos. It really isn't to anyone's advantage if I also have to append to my little post a complete discussion of what is and is not within the boundaries of nutritional theories that have been studied.

I mean... is that... really... what you want...?