"For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord." Romans 8:38,39
"You've got more definition than a dictionary." -me
Current Ignore List (for consideration's sake :D ): Ancients, ImproperOne, A-GAME
I would have to guess that the most common cause is just your gut squeezing some of its contents through the pyloric sphincter. As the above states, when there's less in there, it's more noisy/"bubbly" - hence the growling. If you listen closely sometimes you can hear it "squirt" through.
Not much to worry about really. If you had a mostly liquid meal, and you're not hungry, that's a good example of when it's not a problem - so no, it doesn't always mean you're eating away at your muscle already.
2007 INBF Long Island Experience:
1st Place Novice Lightweight & Overall
Disclaimer: The above can at best be considered an opinion or an offering of advice, and should be treated as such.