If desiring any additional reason to load up on vegetables, this illustration works. It clearly shows why eating junk food will not help a stomach feel as full. Even eating a large portion of animal protein will not help a stomach feel as full. Not feeling full encourages additional eating and thus weight gain.
I first encountered this illustration in the film “Forks Over Knives” and was happy to see it circle Facebook. If unfamiliar with this film, I highly recommend watching it.