Not sure what to do

First option would be to do nothing, given that she is eating twice a day and ? not excessivle losing weight? Though eating less is part of the progression of the disease.

After discussion with your sisters, I would then try testing out an option by going over one day and meeting your mum in the park and either producing a snack and flask of tea from your bag, or taking her to a cafe. If she has a regular routine, you could perhaps employ someone to meet her in the park and do this, though they would probably have to get to know her with you first. I'd also assess how she seemed there - whether she looked thirsty and tired or OK. But employing someone would have to be with your sisters' agreement imo.

I'd also investigate whether she would consider having cards with emergency contact details in her pockets, or some kind of watch/bracelet alarm if you think she would remember to press it.

Yeah, that is the difficulty given that you don't have POA. I guess all you can do really is talk to your sisters again. I do agree with you that it's a long time to go without food though.

Have your sisters given reasons why they don't want carers, btw? - for financial reasons or is there more to it, do you know?

If she is eating a good dinner every night , physically well and not losing weight, I'm not sure you need to worry. I agree with PP that drinking enough is more likely to be an issue because of the risk of bladder problems, low blood pressure (and falls), and other things.

But again as pps say, it really isn't for you to 'handle' directly as you are not on the spot. If you think your Mum needs additional care or input, the way to arrange this would have to be via your sisters and probably at their initiative. So to say to your sister/s "I know you are doing so much and I wish I could contribute a bit more - is there anything I can take on remotely?" [or pay for - if you have the resources and your Mum doesn't]

Do your sisters get respite - are they taking turns? Can you offer to go and stay for a week so they can have a holiday?

Not sure why earlier posters were so rude to OP. Unnecessary. Anyway, the later ones seem better.

My DH doesn't have dementia but he only ever eats two meals a day. Did she used to eat at lunchtime? Maybe this has been her routine for years.

The walking is more worrying but if she's ok with that then I think she's probably ok with two meals. Is there food in the house she can snack on if she feels hungry, fruit etc?

I only eat lunch and dinner I'm hardly ever hungry in the morning, It isn't a big deal really.

My mum is mid 70s and eats twice a day breakfast and dinner although her dinner is at 5, but if your mum is capable of making breakfast and eats her dinner than that's probably enough for her, is she drinking enough during the day ? That can be a worry for older people.

I really only eat breakfast or lunch, rarely both. You can't make someone eat if they are not hungry. A good breakfast and dinner and snacks in the house if wanted is fine I would have thought.

Nothing to resolve
If she fit enough to walk first an hour cclearly surviving on 2 meals.

The short version is if you’re concerned she’s hungry then get yourself there and check. We’re the local ones doing all the heavy lifting, and the whole peanut gallery has an opinion of how they would (but never do) everything.

That is perfectly normal, I don’t expect the elderly to eat 3 meals a day. I have only breakfast and dinner. If she is not losing weight I would let it go. Like me, she has probably lost her appetite. I find a cup of tea and a biscuit fill me up until dinner

It is ultimately the case though.

You don't live nearby, you don't have LPOA.

Your sister(s) do live nearby (or even with your mum - it's not clear) and do have LPOA so this is their responsibility.

There isn't really anything you can do without pissing them off or interfering from afar. You can't arrange carers as you don't have the authority to do so. You aren't there to physically cook a meal for her yourself and for all you know she wouldnt even eat it if you did. There's obviously all sorts of meal deliveries and sandwich options but if she won't eat them it's pointless organising them. I'm sure your sisters will have tried them already... so at this point why do you think anything you do will be perceived as anything other than criticism by them? Even if that's not what you are intending?

Best bet is to get your sisters to agree she needs to eat around lunch time.
Could you make sure she has some snacks in ... biscuits, cakes, nuts, fruit?
Otherwise I'm not sure if you can make arrangements as you say she may not be in when they come.
Try talking to somebody at Age UK, they will have some suggestions I bet.
Good luck and try not to worry, as long as she's not losing weight too much.

As a diff perspective...
while i can see why you are surprised / unhappy but I dont think this is that unusual for old people...
My mum and most of my aunts and uncles aged 70-90s eat twice a day most days... old people need less cals 🤷🏻‍♀️

Also I'd be careful your sisters are prob ultra sensitive as very are dealing with it day in day out.
Unfortunately your voice has less weight as you aren't giving the care ...

That's what my DM said as well. She was going for a walk. She loved walking.

And then there came the time she couldn't find her way back and couldn't remember her address. She was missing for at least 6 hours and got brought home by a very kind man who had found her in distress about 3 miles from home - way off her usual route. He persuaded her into his car and drove her around until she recognised the road, and then he knocked on doors. We were lucky - the weather was dry and the chap was a very kind man.

My Dad also minimised. Was happy to leave her alone at home, long after she couldn't remember where she lived. We tried putting trackers in coats, handbags etc. But DM had a knack of finding them and taking them out.

I'm not saying this to scare you. I'm saying this so you realise that dementia is an ever changing situation and seemingly one day they can remember the route home and the next they can't.

You don't, because you don't have poa

No point having lunchtime carers calling if she might be out.

Both my parents had dementia, and the pickles they got themselves into make not eating lunch pale into insignificance. She’ll not starve if your sister is going in every day to give her dinner (Every day!!! After work!!! Don’t piss her off, she’s a star).

If you feel she is safe to walk to the park for an hour then surely she has the capacity to decide if she wants to eat lunch or not.

I would be more concerned about her walking alone to the park if her dementia is bad enough to forget to eat, rather than just choosing not to eat lunch.