I have found that rewarding myself with food based rewards is counter productive. It just makes me want those things that I can’t eat on a regular basis. So I have adopted a non food based reward model. As I achieve my reward milestones, I give myself things other than food. For example when my BMI drops into the “over weight” range I will buy myself a new tripod for my camera. For smaller milestones it might be a book or magazine subscription.
So, try to find a reward system that does not hinder your efforts.