This is a wonderful forum and resource.
My father-in-law is in his 80s, and has dementia. My wife's family is caring for him at home.
I don't know the right thing to do. It seems very clear to me that my father-in-law is not enough calories. My in-laws are incredibly loving and devoted, but I have not been able to convince them that Daddy would benefit from eating more calorie-dense foods, like nut butters, or even just some fatty things like ice cream. Daddy has little energy, and is often listless and depressed. By my reckoning, he probably eats no more than 1200 calories per day.
How can I help? His dementia has left him severely mentally and physically disabled. Is it better to simply allow his life to fade? I don't believe in keeping people from a natural death.
If you are not doing the caregiving, giving advice can be really annoying to the caregivers. Offer to take care of your father in law for a day. Or for a weekend. You may then have a better idea what they are up against.
Also, it's not uncommon for those with advanced dementia to eat normally, but still lose weight. It's a normal progression of the illness and sometimes even adding calories will not help the person stop losing weight.
It also could be that this patient has chewing or swallowing issues. As long as he was being cared for by his family and not being neglected, I think I would trust their plan of care and treatment, unless they asked for my input.
Do you know if he is on Hospice?
Does your father-in-law have a sweet tooth or did he always crave salty snacks? Try taking him something that he's enjoyed in the past.
Drinks like Boost and Ensure are helpful too.