1,000 calorie diets ... third group gained 0.24 lbs / day

I noticed I was confused. This doesn't seem consistent with the results of the Minnesota Starvation/Semistarvation Study. I went to Wikipedia.

Kekwick and Pawan, 1956 conducted a study of subjects consuming 1000-calorie diets, some 90% protein, some 90% fat, and some 90% carbohydrates. Those on the high fat diet lost the most, the high protein dieters lost somewhat less, and the high carbohydrate dieters actually gained weight on average. Kekwick and Pawan noted irregularities in their study (patients not fully complying with the parameters of the study). The validity of their conclusions has been questioned, and follow-up studies over a longer duration concluded that these temporary differences were due chiefly to changes in water balance (citation)

My prior consider it quite ludicrous that you can gain weight eating at a 50% deficit, no matter what your macros. The criticisms seem reasonable enough to explain the effect.

Note that the link in the citation claimed that when told to cut out carbs and eat as much protein and fat as they liked, "In all subjects, there was a reduction in calories ranging from 13% to 55% during the time they were consuming the low-carbohydrate diet."