Food guarding usually begins with the dog growling, then escalating to snarling and even snapping in the air as a threat. If these behaviour is ignored, and the dog has enough confidence, bites may result. If the dog owner punishes food guarding behaviour, the aggression can escalate quickly as the dog is now also becoming worried about aggression from the owner.
We can prevent food aggression in puppies by teaching them that hands come to give, not take away. This is done by luring them away from what they are eating with a titbit that is much smellier and tastier than the food the puppies are eating. While the puppies are concentrating on the titbits, the food or chew that they are eating can be removed. The titbit is then given to them before the food or chew is replaced. If this happens regularly, the puppy will soon learn that human hands come to give rather than take, and so there is no need to be aggressive.

Note : Feeding puppies from the same bowl causes them to compete for food which can teach them how to be aggressive over food from an early age. This will cause food aggression. Feeding each puppy from a separate bowl helps prevent this.

If your dog is growling, biting, snapping or attacking over food, you will need professional help from a pet behaviour counsellor in order to solve the problem safely and successfully. The solution lies in teaching the dog that approaching human hands are good news rather than bad, but this needs to be done very carefully. It is important to solve food aggression problem rather than just managing it in case someone, particularly a child, approaches unexpectedly one day while the dog is eating.
Until you can get help, try hand feeding, feeding in a different place, scatter feeding which reduces the amount of food in one place and placing food inside strong toys so that your dog has to work to get the food out. Care should be taken to leave the dog alone while he eats until you are able to tackle the problem with a professional. As well as making sure that your dog is safe around food, it is also important that he should learn not to guard bones and chews. This needs to be done in similar way, patiently teaching your dog that your hands come to give, not take.