What's the difference between an addiction to Heroin or Crack and an addiction to Nicotine or Bad foods?

I mean besides the obvious difference in the severity of health risks.

Are the properties between addictions different at all? I go through maybe 2 or 3 periods a year where I can’t stop eating McDonald’s.. I consider their food evil but I always go back to it. I can say with a measure of certainty right now that even though I hate McDonald’s I’m sure to go back again soon. It would seem that I’m addicted to it in much the same way that a recovering Heroin addict may consider themselves still addicted to that narcotic.

The substance is obviously different. McDonalds is less dangerous and less dramatic to indulge in. But the addiction itself.. I’m not sure it’s any different?

Enlighten me?