I’ve seen lots of critiques of McMansions but I can’t recall seeing one that suggests they are bad for your health:

Quite the infographic but I think it (perhaps intentionally) invokes McMansions to introduce some negative connotations and avoids the bigger context: these are problems across American society, whether you live in a big house or not. Some of these are tied to sprawl more broadly with its dependence on cars, on a shift toward eating out and more sedentary jobs, building homes in general, and a growing emphasis on media. This could fit with a common critique of McMansions: they are part of larger patterns of excessive consumption.

In the end, your McMansion is not killing you much more than “average” American contexts are.