I'm a believer in the 'moderation' concept; junk food once in a while won't kill you.
Yep, I agree. What ain't necessarily good for the body is likely good for the soul, once in a while. Problem is, what used to be a "treat" (pop, chips, etc.) has turned into a daily diet for too many kids, and some adults. Granny used to say, "All things are good, in moderation."
My daughters went to school with too many kids who lived on a large bag of 'tater chips and a 2 litre bottle of cola for lunch, virtually every day. That's what I call a problem. My kids ate the same stuff, but it sure as hell wasn't every day! Maybe every week...
Bottom line? Treat the treats like treats!