Dogs that guard food or an object are not bad dogs!
They have an issue that can be changed using a good behavioural plan once the reason and dog have been assessed.
Trying to assert your authority and be the TOPDOG won't work.
The way to deal with it is to change the dogs mind as usually the dog is insecure not dominant.
Ask for help even if it's a puppy showing any sign of growling round food and items.
If left the risk of a bite is high.