Should your weight be determined on what's y for you or healthy for you?

At an adult age. I'm just saying some girls look good thick but its not healthy for them and some look sickly skinny but its there healthy weight for their height. WAIT a minute who made this health chart anyways pfft.I Sould be 155-160 at 5"6 DOC said but I like me at 170 more curvy...Not fair.