@karina77 I can totally sympathize with you, it is so frustrating and annoying to have someone being overly controlling of what you are doing. Try to remember that he is doing it because he loves you and is concerned about you.
You don't say how old you are, but I presume from the "77" that you may be 42, old enough to know for yourself what you should be doing. Have you not been doing the recommended things regarding diet and exercise? Perhaps you have not since you have to force yourself to eat. Is it possible that is causing you to not do the right things, causing him concern?
If you are confident that you are doing what you should be doing, then bring him to the doctor with you so he can hear it from the doctor, that you are doing the right things on your own.
I really do feel for you and hope you can work this out with your father. As I said above, try hard to remember that he is simply concerned about you. You surely do not want this to cause a permanent rift between you and your father.