Father will not eat. What do we do?

Have you considered a psychiatrist who specializes in anorexia? I know that we tend to think of it as a disease that afflicts young women but it sounds as thought that is what he has, at least in part. Bottom line though is that he has to want to improve, I hope he is at least on an antidepressant?

If he has a feeding tube he can't starve himself to death. What were the reasons the doctors gave to putting in the feeding tube? I seldom see that done when there isn't a medical reason for it. @cwillie has a good idea. If the doctors have done all they can do then seeing someone who specializes in anorexia may help.

My grandmother did something similar while in a rehab facility for a broken hip. Was in her 90s but full mental capacity. She wouldn’t eat and lost 30 lbs fast— which she insisted was “just water”. She kept saying she wasn’t hungry. What it came down to though, is that she was just angry. Hated being laid up at the facility (which even she had to admit was a nice place, and it was), mad that she couldn’t call the shots. She had no way to express it, so that was her outlet. Refused Ensure or any kind of liquid food. Would literally make a face and turn away, like toddlers when you try to feed them vegetables. It was maddening. We had to flat out tell her that if she didn’t eat, we’d have to do the feeding tube or she was going to die. Death was her worst fear, so she gave in and began eating... not enough still, but better than nothing. Would eat a piece of lettuce off her plate with tiny child like nibbles. Was her means of control.

Sometimes taking many different medications can affect your appetite.
You can't force him to eat. If he is okay with the feeding tube, then that
is pretty much all you can do. If he becomes adamant about removing the
feeding tube, then I would remove it and let nature take it's course.

My Mother has eaten a real meal for 3 months now, but she is 91. I
decided NOT to put a feeding tube in her. If you research this, you will
see that it prolongs death and can be very miserable for an elderly
person. Good luck, it's always difficult to deal with these situations.
Did your family ever talk to your Dad about what he wants for when
he declines? It's always good to figure out if you want to have a DNR
in place, a feeding tube administered, ongoing hospital visits, etc.

Today many elderly folks are kept alive by unnatural means and I think
it is sad to prolong an elderly persons life when they have no chance of
quality of life. I've told all my siblings if every anything happens to me,
not to have the doctors use tubes and machines in order to keep me,
alive. I want everything to be natural. If I can't survive that way, then
I will die naturally. Just my opinion.