Is it common for someone with dementia to forget they have just eaten?

When my mom was going through that phase, I feed her tiny meals on a tiny plate. That way I could give her lots of small meals rather than 3 large ones. If she asked too close after eating, I would come up with a task we needed to do before it was "lunchtime"...let's dust the living room then we can prepare lunch... Stretch things out so she only eats every 2-3 hours and only small amounts.

My dad has his frozen meals delivered to the house every week, he was fine with this. But lately when I check his freezer he has only a few left to last him the week. He swears blind that he does not have more than one meal per day. One day when I checked, he must have eaten three... I even tried putting stickers on each meal with the days of the week on, but that didn't work, he just ignored the days and took the one he wanted and still managed to eat an extra one. I have started ordering more meals and storing the balance in another freezer he has upstairs for emergencies, he can't remember he has it. Now I thought of just putting two days supply in his kitchen freezer, but I know what will happen he will eat both of them... If I go up every day and give him his meal, I can guarantee he will phone me later in the day to say he has no meals left in his freezer even though he would have had one for lunch.
His tablets are in a device that opens up each morning allowing him only to take them once a day, thank goodness for that as he would be over dosing.
Has anyone else had the same problem.

My cousin's memory loss of what she had eaten started early. It was one of the first things she lost. As a result, she hardly ever ate and seemed to have no appetite. Even in regular Assisted Living, she would refuse to enter the dining room without an escort, however, being on a schedule for meals and snacks that they established for her in Memory Care got her appetite back and now....man, she has a very healthy appetite and eats just about anything.

She's always hungry, though she eats nice meals and 2 snacks per day. She's still very thin, though not underweight.

I would be aware of your mom weight and whether she gains weight easy,, since that can have negative side effects and effect their comfort level, but if she's not obese, I'd provide nutritious food whenever she asks, within reason.

Dementia patients have so little in the way of control and pleasure. I like to cooperate with her requests as long as it's not to her detriment.

Thanks to all of you for your feedback. I had more or less figured that it was normal. It's just that I worried about her not feeling full, right after eating. It's funny, but while she is eating, she will say "this is too much food, I can't finish it all". Then fifteen minutes later she is asking for it all over again.

Yes, it is very common. My mother developed a long-suffering expression on her face as I went back and forth clearing the table. Then she said: "are we having supper tonight?"

Yes even if their empty plate is right in front of them
My mom loves breakfast so I would let her have another bowl of Cheerios - her cholesterol is better than mine

Definitely possible. My mother can't remember what she had for breakfast by fhe time she's finished eating it unless fhere are still leftovers from it in front of her.....but she rememvers evenfs from 50 years ago. It's just the nature of the disease. And if someone was especially focused on eating (like my mom), the it's even easier for them to be constantly focused on food once the dementia kicks in....it's usually the only scheduled thing they can remember, so that's what they cling to.

My MIL would eat 24-7 if there was food in front of her, and she is skinny! When we sit down to eat she gets a plate full, but if anyone has something on thier plate she does not she asks for it! Even jelly packs at restaurants.. like she is going to put it on her eggs? And they can;t leave candy or cookies out or she is trying to sneak them, askes for them... FIL and BIL have to hide things! When we had them at the river they go outside and I bring breakfast out.. a plate of assorted breads, a bowl of fruit.. for everyone. She will keep eating until I sneak the plate away!

My Dad will forget he had lunch if he is in a situation which isn't routine for him, such as a doctor appointment.

Yesterday Dad was in the ER for a fall early evening, and he said he didn't have lunch... I knew he did as the caregiver he has for that day loves to cook and no way would she leave without my Dad being fed a hearty breakfast and lunch. There was no way I could convince Dad that he had lunch so I just gave up and tried to talk about something else.

Well, judging by the comments on this forum it certainly isn't uncommon. Often they lose the ability to understand what the time is so they are uncertain when it is mealtime, or they lose their appetite or are unable to tell if they are hungry or bored or what is bothering them so they obsess about eating, and they lose short term memory so the truly don't remember having eaten. You will never convince her that she has already eaten so if she is on the slim side let her eat whatever snacks she wants, if she has dietary restrictions leave her lower cal healthier foods.

Yes, it is common. What you can do is to use a calendar and have her put a check mark on it for breakfast, lunch, and supper. Then she can check the calendar to see that she has indeed already eaten. She most likely won't believe you, since your reality is going against her own, but maybe she will believe her own calendar. The only challenge is reminding her to check things off while she is eating. This is how I handle my mother's insulin injections. She marks the calendar when she takes her shot. This is good, because 5 minutes later she will have forgotten.