A steadier ground guide to the meal that didn't register. Why it happens, how much of a risk it actually is, and what to say instead of reminding him he just ate. If he takes insulin or a diabetes pill and is confused, drowsy or sweaty right now, check his blood sugar before you read anything else.
Notice the flicker of impatience when he asks for food again twenty minutes after eating. That flicker isn't meanness, it's a normal response to a question that has no satisfying answer, and catching it keeps it out of your voice when you reply.
Before anything else, offer a drink, unless he has swallowing trouble or is on thickened fluids, in which case follow whatever his speech therapist set. Thirst gets read as hunger often enough to be worth ruling out first. This is care-home practice rather than trial evidence, so if it does not work twice, stop trying it.
The usual cause is simpler than it looks. The meal happened and the memory of it did not form, so there is nothing to retrieve. He is not testing you. He also cannot place the meal in time, which is why telling him when he last ate helps less than telling him when the next meal is.
Underneath that, the request is often not about food. Repeated asking is frequently a way of seeking reassurance, and someone who lived through real scarcity may need to hear that food is coming rather than that food already came. Boredom drives it too, so if the asking clusters when he is alone and stops during company, that is your answer and it is not a menu problem.
One distinction matters more than any technique. In Alzheimer's-type dementia the appetite machinery is intact and the problem is memory. In behavioral-variant frontotemporal dementia the drive itself is altered: binge eating, a pull toward sweet and starchy food, increased drinking and smoking, and putting non-food items in the mouth are formal diagnostic features rather than side effects. That version responds less well to reassurance, since he may agree he has eaten and still want more. If that is the picture, environmental control means locking away alcohol, medicines and cleaning products rather than locking away food, and keeping a stocked snack station he can always reach. The aim is to make the safe options the easy ones, never to make him unable to get food.
It is worth being honest about the danger, since fear pushes families into restriction that does more harm than the eating does. Stomachs do not rupture from a second sandwich; the world literature holds around three dozen cases of spontaneous rupture from overeating since the 1960s, about half of them in people with eating disorders. What can happen with genuine binge eating is a painfully swollen, hard belly with vomiting, which needs an emergency room. The everyday risks are narrower: blood sugar if he is diabetic, and choking or food going into the lungs if he eats fast. Weight gain is real, slow and manageable, and across dementia as a whole weight loss is far more often the problem.
Almost everything below is expert consensus rather than trial evidence, since the research on eating interventions in dementia is thin. That is worth knowing, because it means you are allowed to drop what isn't working.
Note when he asks, who is in the room, and whether he actually eats what arrives. Asking without eating means the request was never about food. Weight moving down while requests go up is a different problem and belongs on the phone. If he is diabetic, keep the log where whoever manages the diabetes can see it, since a changed eating pattern usually means the regimen needs revisiting.
You are allowed to say yes. A second piece of toast is not a failure of caregiving, and most of the harm here comes from families frightened into restricting someone who was never in danger. If the day ends with him fed, unhurried and unembarrassed, the day worked, whatever the count was.