Not a weight loss 'diet', just to be clear. It also has no connection to financial issues or lack of availability locally.
My Dsis and her DH (both in late 50's) used to eat meals she prepared, mostly fresh but affordable. What I'd call an average, healthy diet. Over the past decade or so her DH's tastes changed, eventually reaching a point where they accepted not sharing meals together any more as she preferred to carry on as usual. He is a decent guy, doesn't have any health issues and doesn't seem to have changed in any other way.
He jokes about how he eats as he can see that it's a bit different to the rest of the family, so isn't uptight about it outwardly. It's just a bit unusual in how it has evolved over recent years.
There is also nothing 'wrong' with his food choices exactly, it is more the attitude to it that has altered. Some examples:
Will only eat tinned food, including very cheap soup, beef, baked beans, meatballs, peas, hotdogs (B&M's, etc). The meat meals are almost always served with a tin of peas or baked beans. Often the hot dogs float in tins of chicken soup. A few buns/rolls accompany the meal.
This never changes and has a strict routine, so the rotation of them never varies. There is no interest in regular (un-tinned) vegetables or fresh meat, cheese, eggs or fish. He doesn't eat dessert of any kind nor snacks, except a few chocs at xmas. He does drink alcohol twice per week, usually red wine or beer.
No food allergies of digestive issues and is only slightly overweight.
Food choices are really personal and this isn't a critique or cheap shot at him. We all have our foibles. I was watching a few episodes of freaky eaters, or something of that ilk, and noticed a few younger people who could only eat chips or only ever ate sandwiches, etc. He does remind us of this a bit!
Like I say, otherwise a pretty regular guy, although quite routine focused. I wouldn't' say it has badly impacted their relationship but Dsis LOVES cooking, and whilst he always compliments her on that, he will politely never join in - and I mean never!
My thoughts are that he doesn't like fuss and prefers a very quick way to prepare food (just warm it up!) but it puzzles me why he doesn't occasionally enjoy eating anything with Dsis at all. What I wouldn't tell my Dsis is that it looks weirdly 'bachelor' like to me, as if psychologically he is pulling away from a fundamental thing that pulls people together, if that makes sense?
Has anyone experienced this gradual shift in a middle aged person, and does it strike anyone as a bit odd?