Is weight loss in dementia normal?

My father had Alzheimer's for 9 years 19798 to 1987 he went from 180 to 65 lbs the day he passed. We cared for him at home where he passed away. Speaking to the Neurologist, she stated the weight loss was not from the Alzheimer's, it was from a secondary illness, such as thyroid dysfunction or cancer of some kind. His Dementia was in stage 5 last one when he started losing wt. so we had no way of helping him except feeding him well, and he ate well until the last 7 days went into coma from uri. We found out later he had thyroid dysfunction he had been on meds for when he was going to the VA. We had No idea. Please if you can check into your fathers medical history and see if that could be an issue.

My grandad is 97 and just over 6ft. He went from weighing 12st to just over 9. I think alot of it was to do with him forgetting to eat when we didn't realise how bad he was and also the fact that he has gone from being incredibly active to barely moving out his seat. He's probably lost alot of weight in muscle as he has never been a heavy man. He is now eating alot better than he was and we are finding ways to up his calories. Perhaps this could be the same situation for your dad?

My dad has dementia and went from a very fit 165 lbs. to 125 lbs. in a relatively short time frame. He has gained a little back but still is below the weight of his entire adult life.