Who decides they "need it to survive"?

Do you understand that in some gaining weight can trigger a lots of issues? Lots of people are prone to eating disorders, body issues...

And it's okay to say gaining weight is NOT acceptable side effect and person should not be bullied into staying on drugs that cause this.

Again, it's up to them. To some it's okay... BUT if the person is not okay with it, they are likely toss the med at one point, thrusting a nasty withdrawal upon themselves. They can develop ED.