That's a very good question, MickeyKat, and I have two answers.
First is the easy one... replace it with knitting, crafting, talking to friends on the phone, exercise, reading, biking, gardening, and all those other things you can "DO" to keep your mind/fingers/body occupied.
The second one is harder. For me, I have always eaten as a soothing mechanism. To soothe sadness or frustration or anger or boredom. Basically, I'm soothing some feelings and making myself feel better (temporarily).
An important person in my life, who is a recovering addict told me that recovery is hard, because you have to learn to sit with your feelings and not numb them away, and that it's okay to have uncomfortable feelings and just HAVE them, and not try and make them go away.
So my 2nd answer to "what did I replace food with?" is that I am replacing it with learning how to live with uncomfortable feelings, learning how to just sit with discomfort and feel it and move through it and then out the other side. It's hard but I want to practice it as much as possible. I feel like if I don't, I will just end up back in my original spot 3-5 years out. And I don't want to do that.