This sounds more like the results of nutritional deficiencies to me rather than caloric restriction.
I know because I eat less than 1,600 calories a day every day but Saturday, and I am rarely all that hungry and do not experience any of the observed effects cited in the article.
Given the diet they were on, there’d likely be several very important vitamins nearly completely omitted, ineluctably leading to the increasingly bizarre behavior.
If I wanted to lose more weight (I don’t), I think I could do 1,200 calories a day without much additional hunger or even really noticing.
I just don’t buy that that study was studying what the FA community would like you to believe it was studying.
Sounds like classic vitamin deficiency to me.