Learn Spanish (Spain): Ya no como carne porque me he hecho vegetariana. - I no longer eat meat because I have become vegetarian.

The verb hacerse is used for changes that are voluntary and involve an active effort, especially regarding professions, religions, or ideologies. Choosing a vegetarian lifestyle is a conscious decision, so hacerse is the right verb. Ponerse is used for temporary physical or emotional changes (like getting sad or blushing).

Why is there a me before he hecho?

The verb for "to become" here is the reflexive verb hacerse. You need the reflexive pronoun me to show that the change is happening to yourself. Without it, he hecho just means "I have made" or "I have done". Notice that the pronoun goes right before the conjugated helper verb (he).

If I am a man, do I still say vegetariana?

No, you would say vegetariano. Even though it follows a verb, vegetariana acts as an adjective describing the subject here. It must agree in gender and number with the person who has changed, so a male speaker changes the ending to -o.

Can I translate "not anymore" by putting ya no at the end of the phrase?

No. Unlike English where we often put "anymore" at the end of a sentence (I don't eat meat anymore), in Spanish ya no generally goes right before the verb it modifies. You must say ya no como carne.