title: Human brain mass: similar body composition associations as observed across mammals.
abstract: OBJECTIVE
  A classic association is the link between brain mass and body mass across mammals that has now been shown to derive from fat-free mass (FFM) and not fat mass (FM). This study aimed to establish for the first time the associations between human brain mass and body composition and to compare these relations with those established for liver as a reference organ.
  
  
  METHODS
  Subjects were 112 men and 148 women who had brain and liver mass measured by magnetic resonance imaging with FM and FFM measured by dual-energy X-ray absorptiometry.
  
  
  RESULTS
  Brain mass scaled to height (H) with powers of ≤0.6 in men and women; liver mass and FFM both scaled similarly as H(~2) . The fraction of FFM as brain thus scaled inversely to height (P < 0.001) while liver mass/FFM was independent of height. After controlling for age, brain, and liver mass were associated with FFM while liver was additionally associated with FM (all models P ≤ 0.01). After controlling for age and sex, FFM accounted for ~5% of the variance in brain mass while levels were substantially higher for liver mass (~60%). Brain mass was significantly larger (P < 0.001) in men than in women, even after controlling for age and FFM.
  
  
  CONCLUSIONS
  As across mammals, human brain mass associates significantly, although weakly, with FFM and not FM; the fraction of FFM as brain relates inversely to height; brain differs in these relations from liver, another small high metabolic rate organ; and the sexual dimorphism in brain mass persists even after adjusting for age and FFM.
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA 70808, USA. steven.heymsfield@pbrc.edu
authors.forename: Steven B
authors.initials: SB
authors.lastname: Heymsfield
authors.forename: Manfred J
authors.initials: MJ
authors.lastname: Müller
authors.forename: Anja
authors.initials: A
authors.lastname: Bosy-Westphal
authors.forename: Diana
authors.initials: D
authors.lastname: Thomas
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D001823:Body Composition; D049628:Body Size; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009928:Organ Specificity; D044465:White People; D055815:Young Adult