I can only speak for myself, but I have not obsessed about food on the diet at all. If I start to think of food, I just try and push it away. I think part of my being able to do that was I had about 8 weeks to psyche myself up before the diet started as I met my LLC right in the midst of the holidays. I spent weeks imagining myself doing the diet, and not eating. I did an awful lot of difficult mental work before I even began the diet. It was hard work, but by the time the diet started, I was so fed up with food, I didn;t even have a last meal! I really couldn;t wait to stop eating. Then, once I started, whenever a thought pops in my mind, I just swtich it off, because I know its not an option, so why entertain the thought?
Now, after months on the diet, I think about food, as in the future. What I will prepare. How I will shop. What I will continue to buy pre-made and what I will change to making from scratch - those orts of things. Just sort of picturing new habits and a new lifestyle, etc.
This certainly does not mean to sound glib, but we are in control of what we think about, and we can stop or start a thought if we really want to. So I would suggest, just tell yourself there's no point wasting time thinking about something you are choosing not to have, and switch to thinking about your future. Your goals, the acheivement you are pursuing...those kinds of things. Pretty soon you will constantly have your eye on the prize you won't want to think about food!
Good luck!