Carter and his food dish

Food 'guarding' behaviour, in my view is a sign of insecurities, frustration, lack of trust, and lack of bond and NOT A DOMINANCE ISSUE as many people seem to believe.

This is how I usually deal successfully with this 'problem':

Aggressive, insecure and food possessive dogs start with being fed from my hand only. They do not have a food bowl at all and when the problem is really serious they do not have a water bowl neither (be careful in the summer when it's hot).  All food and all water comes from me. During the meal time his entire serving is in my possession, secured in a poach... We sit down, just the two of us and we have a great time sharing the meal time. I do not have any  expectations from the dog, I do not tell him to be gentle or good or to sit or do anything to receive his food.  He is free to eat happily his entire meal from my hand... I want him to feel secure, I want him to experience my hands and my time with him in positive, non-threatening way.

After several days, when the dog is really comfortable with my hands and eats his meals eagerly and happily, I put his empty food bowl at my feet during our meals together.  I would start to alternate dispensing the kibbles directly to his mouth and  dropping them into the bowl for him to eat.

 Again, I want the dog to feel comfortable and happy.  More and more food goes into the bowl at my feet.  More and more often my hand is in the bowl when the dog is eating and my hand always contains food.

The next step: we start with some food in the bowl at my feet and when the dog starts eating I start adding more and more.

The next step is to move a bowl one foot, then two feet away from me so I have to "sort of" approach the bowl, reach farther, to add  more food. At this point I also introduce "better" tidbits (like sliced chicken wieners or liver, or kidney bits...) which I only add when I have to "approach" his bowl even if it's only 2 feet away from me.  I want the dog to experience only WONDERFUL things when I'm around his dish.

If at any time during this "training" dog shows any discomfort, tension or growling I ignore it and move a step back to where the dog was fine. I was obviously going too fast.  Every dog has his own timeline which we have to respect...

If properly done it is amazing how fast the dog becomes happy to see you approaching his food bowl.

Our new rescue pup?

Within just few days  I was able to put my hand in his food bowl and pet him when he was eating and all I was getting were happy tail wags.  He was one of the easiest "food defensive" dogs we had in a while.  He got adopted  and there are absolutely no problems in his new home.
 
Couple of important points to remember while dealing with this problem:

NEVER, EVER CORRECT THE DOG FOR GROWLING OR SNAPPING AT YOU, there should be absolutely no confrontations of any kind with the dog...

DO NOT make another common mistake of trying to reassure your snarling dog by telling him that he's a good boy.  Just ignore him at that moment.  Otherwise, telling him "that's ok", "good boy", "I won't take your food", or any other words meant by you to reassure him and calm him down, create a confusion in his mind.  In fact, this behaviour is NOT OK and he is not a "good boy" at this moment.

All our communication with our dog should be crystal clear.

Through his behaviour our dogs are always communicating something to us, and it is our obligation as their partners and friends to listen and respond in a constructive and very clear way.