Say a small prayer over ever meal, and even your snacks. Ask that this meal be nutritious to your body and give thanks for it. And have faith that it will. This might sound funny, but you would not give thanks for a Snicker bar would you? So, if you make a HABIT, you should be less likely to "CHEAT."
Did you ever see someone in a restaurant or across the break-room table bow their head and say a small prayer over their food? And then think about their commitment, and know that their public display of thanks was genuine? Same goes in your commitment to eating healthy.
Now, if you are doing this as a joint project with your spouse, then join hands and pray together. Also, if you have in your plan a "free meal," also ask blessing over it. I promise, it will be more fulfilling because of your commitment. And, may cause you to push the plate away before it is all gone. Call it "PSYCHOLOGICAL", call it "SPIRITUAL", call it HOG WASH, whatever, IT WORKS...
So, truly be thankful for your food. In a short time, you will see that it works, EVERY TIME.