Body composition in anorexia nervosa:meta-analysis and meta-regression of cross-sectional and longitudinal studies

Objective: Clinically, anorexia nervosa (AN) presents with altered body composition. We quantified these alterations and evaluated their relationships with metabolites and hormones in AN patients longitudinally.Method: In accordance with PRISMA guidelines, we conducted 94 meta-analyses on 62 samples published 1996-2019, comparing up to 2,319 pre-treatment, post-treatment, and weight-recovered female AN patients with up to 1,879 controls. Primary outcomes were fat mass, fat-free mass, body fat percentage, and their regional distribution. Secondary outcomes were bone mineral density, metabolites, and hormones. Meta-regressions examined relationships among those measures and moderators. Results: Pre-treatment female AN patients evidenced 50% lower fat mass (MD: -8.80 kg, CI 95%: -9.81, -7.79, Q = 1.01 x 10-63) and 4.98 kg (CI 95%: -5.85, -4.12, Q = 1.99 x 10-28) lower fat-free mass, with fat mass preferentially stored in the trunk region during early weight restoration (4.2%, CI 95%: -2.1, -6.2, Q = 2.30 x 10-4). While the majority of traits returned to levels seen in healthy controls after weight restoration, fat-free mass (MD: -1.27 kg, CI 95%: -1.79, -0.75, Q = 5.49 x 10-6) and bone mineral density (MD: -0.10 kg, CI 95%: -0.18, -0.03, Q = 0.01) remained significantly altered. Discussion: Body composition is markedly altered in AN, warranting research into these phenotypes as clinical risk or relapse predictors. Notably, the long term altered levels of fat-free mass and bone mineral density suggest that these parameters should be investigated as potential AN trait markers