It's because they know that these teens will grow into desirable adults, and have an easier time of puberty and maturation than they did.  Their social lives will be better, and their entire life prospects will be brighter. Hams just can't stand their envy, and want to make it seem as if their fattness during youth was because they "didn't starve themselves".  Surely that's the only way someone can look like that, right?