Do anorexic patients lose skull mass and brain tissue and bones get thinner?

Anorexia: Ongoing anorexia will demineralize bones of all sort. Brain is less likely to shrink than other tissues such as muscle, tendon, skin, and adipose.

They gain: sharper appearing facial features due to loss of subcutaneous fat. Cortical bone may become less dense due to failure to lay down matrix and hydroxy appetite crystals (catabolic state leads to loss of structural proteins). Eventually brain protein is broken down to be converted to glucose ( maintain energy levels that would otherwise be coming from other sources (carbohydrate, glucose, fat etc)