i dont get this fat joke?!?

[lmfao <3 bra]

so my friend in high school told me this joke im in 7th grade so i dont get it.
he said i love fat people jk jk jk then he said its o-mazing
whats that mean?????
if it isnt a fat joke then wats it mean?

 

[julia is so awesome]

they dont wear size 0. idk