Comment by sdoering

What I know from personal experience and learned a bit through knowledge osmosis (my better half studied ecotrophology/nutrition) is that many people underestimate how the body adapts to a "new normal" of caloric intake when this is well below basal metabolic rate/consumption.

On the other hand, the body also likes to get essential amino acids, if it does not get them from food, from the body's own muscle mass. This leads to a reduction of the own muscles and to a low basal metabolic rate.

I cannot judge whether one of the reasons is true, that would be the job of a good (!) nutritionist. Unfortunately, at least in Germany, the term is not protected and anyone, regardless of education, knowledge or experience may call himself so. Here there are really (especially on social networks) really many false claims.