In UD for food refusal the dog has to completely ignore all atemps to feed it. When you leave the dog the only command that you can give is STAY. One way to teach it is when you have another person offer the food, you leave the dog with the command STAY, then thfey approach if the dog goes for the food the person offering trhe food very gently pushes the dog's head away,with a very soft verbal correction. I hope this helps. In realation to dogs not taking food or anything else on a walk the LEAVE IT command is one of the best things any dog can learn.