>... has there ever been verified science that shows exercise is unhealthy?

Yes, the extremes of endurance have certainly been shown to have a negative effect on heart health, and possibly also colon health, but the amount of exercise required to get into the danger zone here is so high almost no one that isn't a competitive athlete would achieve it. (Although, amateur marathon runners might.)

You could look at the inverse: Not exercising causes the brain to look older. Knowing all of the ways not exercising is harmful is probably a good thing.

But I agree, it would be better if everyone exercised!

And I chuckle at these types of comments.

We know that exercise is good for us, but studying it is how we better understand the different ways it is beneficial for us in a controlled setting.

I see these comments online a lot, just because something might be common knowledge, doesn't mean we fully understand it, nor should be stop studying it.

Good point, but has anyone shown that gravity doesn’t work in general relativity conditions? We move the needle of proof, such that the burden to disprove becomes harder. That seems fine by me, it’s nicer and nicer to see the benefits of exercise.