[EvaH (OP)]

Brian asks:

Why is it that some overweight people seem to be able to maintain a constant weight (without getting heavier), but after they lose weight from dieting they usually return to their previous weight? That is, if they can maintain a heavier weight, why is it more difficult to maintain a lower weight? Would the intake of calories in both cases be about the same to maintain both weights?

What do you think?

[Colin2B]

Would the intake of calories in both cases be about the same to maintain both weights?

What do you think?

No, they are not the same.
The lower your weight, the lower your basal metabolic rate - the amount of energy needed to keep you alive at rest. Also, imagine walking upstairs, the more you weigh the more energy you need to get up there.
People who lose weight often revert back to their original eating level which is too much for their new weight.

[RyomaJiro7]

Because it is difficult to get fat.