Several ghrelin analogs are used to stimulate GH secretion. A common reported effect is increased hunger. This makes a certain sense for a couple reasons. If there's no food coming in, growth prevents tissue loss. And if there's no food coming in, hunger drives one to go hunt for food.
The thing about increased hunger in spite of same ghrelin level following weight loss with a calorie-restricted diet, that's not actually new. We got the Minnesota semi-starvation experiment, where subjects just scarfed down everything they could once the experiment ended. They gained what they'd lost, and then some extra fat tissue. What is new is that the hormone that regulates hunger stays the same, yet hunger is greater. I'm leaning toward a greater sensitivity to ghrelin, maybe due to feedback derived from the neurosis triggered by the calorie restriction. Or, if we also invoke leptin (likely the satiety hormone they mention), then I lean toward a greater resistance to leptin, which should otherwise suppress ghrelin, maybe also a result of some feedback from the neurosis etc. Or, if we also invoke dopamine, we could imagine the calorie restriction had become a learned behavior, where there's little dopamine being released cuz there's little food to trigger this release, which in turn results in a sort of greater demand for dopamine once calorie restriction ends, and this greater demand just can't be filled cuz the new learned behavior (learned during calorie restriction) overwrote the old one of adequate food intake, maybe also a result of the neurosis.
About neurosis. I think it's a sort of trauma. Things learned during trauma stick. It's very hard to get rid of loop thoughts developed during trauma. I imagine the constant thinking about food must have stuck with these subjects, long after the experiment ended. The loop thought here would have been something like "hungry, can't eat, experiment, hungry, can't eat, experiment, etc", on and on every second, day and night for the length of the experiment. It's a very short loop, easily learned at first and easily remembered. Once the experiment ended, the "can't eat" and "experiment" parts of the loop disappeared, but the "hungry" part obviously stayed because it's a natural part of our thoughts, it just became more prominent due to the neurosis resulting from the initial loop during the experiment. The trauma of neurosis amplified the otherwise benign hunger, maybe in both amplitude and frequency, but probably mostly frequency.
I wonder if they asked how often they felt hungry before and after calorie restriction?
On the other hand I only need to think of the two monkeys in a cage. The one who gets his hit only once in a while, he pushes the button all the time. This means that for caloric restriction, if it was possible to push the button all the time, we would. In effect, the effect of caloric restriction observed post-experiment is immediate rather than just post-experiment. This means they should look more closely at the effects during calorie restriction. Who knows, maybe they'll find that experiment somehow unethical. But then again, they haven't deemed it unethical yet and they did find a detrimental effect post-experiment.