@wissem,
Take the clause out, (italicisesd) and reread it.
If you don't want to be fat Sally, you have to
take care of your health and
If you don't want to be fat Sally you have
to (follow, followed to, follow.)
That to in bold is already there whether or not you remove the clause. You don't need another one.
If you don't want to be fat Sally, you have to take care of your health and follow my advice.