Background: Anorexia nervosa is a serious health condition characterized by a significant
low body weight and alteration in body composition components.
Aim: In the current paper, we aim to summarize the available literature concerning changes in body
fat, lean, and bone masses, during anorexia nervosa and after complete weight restoration.
Methods: Data were summarized using a narrative approach based on clinical expertise in the interpretation
of the available evidence base in the literature.
Results: The available data revealed three main findings. Firstly, anorexia nervosa causes a significant
reduction in body fat mass, however it is completely restored after short-term weight normalization
but with a central adiposity phenotype that does not seem to negatively influence treatment
outcomes and appears to normalize after 1 year of normal weight maintenance. Secondly, anorexia
nervosa causes a significant reduction in bone mineral density, but weight restoration is associated
first (≈12 months) with stabilization of bone mineral density, followed by improvements (after ≈16
months); and finally, with complete normalization (after ≈30 months) after normal-weight maintenance.
Thirdly, during anorexia nervosa loss of lean and skeletal body mass occurring in particular
from the extremities rather than the central regions has been consistently reported, especially in patients
with a Body Mass Index (BMI) ≤ 16.5 Kg/m2 however short-term weight restoration is associated
with complete normalization.
Conclusion: Anorexia nervosa adversely affects body composition, however this medical complication
seems to be reversible through the main treatment strategy of body weight restoration followed
by normal weight maintenance, and this should be openly discussed with patients.