Sounds to me like this dog is a rescue if it is new to you but is already two years old. That in it's self makes it more difficult because there may be past abuse with food in the dogs life. You have two options.... one, if you give the dog the food then stay away until the dog is finished (as Carrie stated). Don't leave the bowl down so the dog can graze whenever it wants too. Have set feeding times twice a day. Any other time, the bowl is picked up and nowhere where the dog can get too it. Avoid things that may trigger food aggression such as bones and treats that last more than a minute to chew.

Second choice.... Start positive obedience classes with the dog and then make it work for it's food as a reward. I would suggest an established trainer / behaviorist who can make sure you are doing the training properly. Your goal is to teach the dog that everything good in his life is given by you.

Until formal training can be achieved, just stay away when the dog eats. I really don't think you would be real happy if someone tried to take your food away while you were eating it either.