I eat junk food pretty much every day, but I stay active and I'm one of the more healthier people around, so I've never really bothered with a diet. I'm still skinny, fit, can run long distance, why bother?
The only time I actually eat something properly is on the morning before cricket - never eat a sugary cereal or a snack, always go for a decent breakfast to get started.. like Weet Bix or Muesli Flakes or something decent.