Dad told everyone endlessly about his ketogenic diet to prevent dementia and how he was growing broccoli sprouts and eating red meat and so forth in great detail, but it turned out he had gradually (or suddenly?) stopped being able to manage his own food and was barely eating at all.
His mother had the same thing happen. Apparently, its relatively common in elderly people. If you are calling in on old people, check their refrigerator. Ask them what they had for breakfast. Or lunch or whatever. If you eat with them, do they only have a tiny appetite?
Also, obviously unbalanced fad diets are bullshit unless being used to manage inflammation or diabetes or an actual, diagnosed problem. Low calorie / lpw carb diets are being hyped on YouTube as a panacea for aging.
Thank goodness the "zero grain keto" breakfast cereals are actually made of corn…