My mom's dog Teddie is like this...lol I mean it's really not funny, but it's my dads fault. When they were still together he would egg her on and mess with her while she was eating...

Now she's like that with everything. You DO NOT mess with Teddie when she's eating, sleeping, or chewing on a bone, or has one of her favorite toys. Except me. She growls at me once and point my finger and say NO, BAD GIRL...and that's it...she quits.
None of mine have ever been food aggressive, but I am constantly reaching in and around their bowl to do whatever I want. They'll turn their heads away with a treat if they think I'm trying to take it...but just a firm NO usually gets them to drop it. Even the girls I got as adults are pretty good about everything. Luckily I got sweet ones...