Telling fat people they ought to be thin is about as helpful as telling gay people they should be straight. It took many decades for the medical establishment to recognize that its “cures” for “homosexuality” did far more damage than the imaginary disease to which they were addressed, and that the biggest favor it could do for gay people was to stop harassing them. Fat people are still waiting for the same favor.
In public health, we should be promoting health and working to end discrimination based on body size and sexual orientation, which only serve to make matters worse. *Steps down from soapbox*