Thats what most nutritionists recommend, once a month or less.
The biggest problem is that we live in a franchised nation. Actually, thats not even the main part of the problem. The problem is that out of all the franchised restaurants, maybe 1% of them serve healthy food.
A huge majority of people eat out every day. The options are pretty much always the same and you dont have much of a choice but to eat this crap all the time. Anyone who tries to deny that is a dumbass.