Surely it depends on your lifestyle? If you sit at a desk all day Mon-Fri and do no exercise then I’d say you’re in danger of putting on weight at 1500cals. (Depending on your height)
The old ‘women need 2000 cals a day’ spiel is very outdated IMO and is why we have an obesity problem in the U.K.
You don’t say whether you do any exercise. If you don’t, get out for a brisk, one hour power walk everyday and you might be able to up it to 1700-800? Or an hour run which would be more.
Two slices of toast with butter, washed down with a cup of tea is probably about 250 cals.
Mid morning snack of an apple- 90cals?
Lunch- sandwich of some description with some carrot sticks- 350 cals
That leaves you about 800 cals for dinner. Google says a portion of lasagne is about 360 cals, you could add a load of chips or some garlic bread and salad and still meet the 800 cals. This is obviously just one example dinner.
You definitely won’t starve on the above and your body would soon get used to it. Don’t get me wrong, I’d definitely have relaxed days where I’d have some wine, chocolate and either make up for it the next day or do extra exercise.
But no, I don’t think 1500 cals is unsustainable depending on body type/ height and activity level.