(Of course, you may not be a problem if you are sufficiently self-disciplined, as you seem to be.)

Yeah, that seems right.

But the vagueness involved in the notion of a "piece of junk food" was such that I found I had considerable latitude in determining how many pieces of junk food I ate on a particular day.

I tend to define it roughly as "250 calories of something that is devoid of nutritional value and consumed primarily for taste".