They say that you don't want your digestive system active when you do the pull. I would think its so the enzymes and such can kick into effect in your mouth better when they're not already otherwise occupied digesting your last meal. I don't know. I just started OP therapy but I have tried it before lunch. I don't do it before dinner because I saw a message somewhere saying that can cause insomnia, that you're too energetic afterwards and can't sleep. God knows I don't want to lose any sleep, LOL!