Wow. Interesting. But I think backwards. Food high in fiber leave the body more quickly, as the fiber helps them get digested. Fast food is usually high in fat and protein, which get digested more slowly. But slow release and time release refer to a type of capsule that medication or supplements are packed in that dissolves slowly so everything in it isn't released all at once. And as I said, since the body digests at its own speed, most of this will never come out in the body at all as it will have been evacuated.
Without going and checking on the web I'll give you my understanding :). I haven't heard of time release, but slow release I understand to be high in fibre; foods that release their nutrients into the digestive system rather than straight to the exit regions.
So foods that benefit your body, rather than over-processed fast foods. Maybe the name "fast food" refers to how fast they go through your body rather than how quick you get served
Don't know what you're working on. Time release is slow release. When I managed health food stores the saying about time release was, expensive urine or bowel movements, since the body evacuates before the stuff comes out of the capsule. There's a project for you