This is actually a quite common problem and there are differing opinions on how to address it.
First, what does food bowl guarding look like? There are several stages or levels if you will.
Dog is given food in bowl. When approached the dog will quicken the pace of eating.
The dog is eating. If you approach the dog may stop eating and virtually freeze.
The dog is eating and all of the above may happen or only the freeze. But now the dog may look sideways at you and emit a low growl.
The dog is eating. The dog may present with any or all of the above but now an air snap or lunge is added. Now you have a full-blown guarding behavior and it can be quite dangerous, especially for children.
The long-standing preferred recommendation for this issue is to place your hands in the bowl of your eating dog from day one so they get used to it.
I personally do not recommend nor practice the above. Instead I prefer to keep my dog/puppy from ever practicing this behavior. First because I do not allow it but more importantly because I make sure the dog has no reason to feel it has to guard its food. Other dogs are not allowed to approach an eating dog not do I pressure the dog by being too close. I have found that this way of dealing with potential guarding slowly lets the dog relax as it doesn’t feel threatened. At some point even if another dog approaches it is usually not an issue as the dog has not been practicing guarding and is much more relaxed. Having had multiple dogs for many years I found this method very effective in keeping the peace and keeping everyone safe.
Of course dogs can guard many things including toys, resting places, people, and even some very strange things like patches of grass or rocks. Each type of guarding has a different solution of course.