I have been thin all of my life, and I have gone through time spans where I feel awful about myself. My own sister has called me anorexic more than once. I love eating and food. I just have a fast metabolism.
On the day of my senior prom, I had a stranger walk up and repeatedly tell me that I "needed to put meat on my bones."
People think skinny shaming isn't real, and it definitely is. For children, any slightly shameful comment is dangerous. It will stick with them for life, and that's not okay at all.