title: In adult twins, visceral fat accumulation depends more on exceeding sex-specific adiposity thresholds than on genetics.
abstract: OBJECTIVE
  We recently reported sex-specific percent body fat (%BF) thresholds (males=23%, females=38%) above which, visceral adipose tissue (VAT) significantly increases. Using monozygotic (MZ) and dizygotic (DZ) twins, we examined the influence of genetics on regional fat distribution measured by dual-energy X-ray absorptiometry, above and below these sex-specific thresholds for VAT accumulation.
  
  
  METHODS
  Fifty-eight twin pairs (44 MZ, 14 DZ) were recruited from the University of Washington Twin Registry. Segmented linear regression was used to assess the threshold between VAT mass and %BF by sex and by zygosity. To assess the effect of genetics on VAT accumulation, Dunnett's T3 compared MZ and DZ pairs whether the twin pairs were both above the adiposity threshold or not.
  
  
  RESULTS
  %BF thresholds for VAT accumulation were identified (%BF: M=20.6%, F=39.4%). Zygosity-specific thresholds were not significantly different (p>0.05). If at least one twin was below threshold, DZ twins still exhibited greater within-pair differences than MZ pairs in %BF (p=0.023) but not VAT (p=0.121).
  
  
  CONCLUSIONS
  Using a twin study approach, we observed no difference by zygosity for the threshold as which VAT accumulates. Additionally, for the first time we observed that while total BF is influenced by genetics, VAT accumulation may depend more on whether a person's %BF is above their sex-specific adiposity threshold. These results suggest that there may not be a genetic predisposition for VAT accumulation but rather it is a result of a predisposition for total fat accumulation.
authors.affiliation: Department of Medicine, University of Minnesota Medical School, MMC 101, 420 Delaware St SE, Minneapolis, MN 55455, USA. Electronic address: bosch041@umn.edu.
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Bosch
authors.affiliation: Department of Medicine, University of Minnesota Medical School, MMC 101, 420 Delaware St SE, Minneapolis, MN 55455, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Chow
authors.affiliation: School of Kinesiology, University of Minnesota, 1900 University Avenue SE, Minneapolis, MN 55455, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Dengel
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Melhorn
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Webb
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Danielle
authors.initials: D
authors.lastname: Yancey
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Holly
authors.initials: H
authors.lastname: Callahan
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Mary Rosalyn B
authors.initials: MR
authors.lastname: De Leon
authors.affiliation: Simmons College, 300 Fenway, Boston, MA 02115, USA.
authors.forename: Vidhi
authors.initials: V
authors.lastname: Tyagi
authors.affiliation: Department of Medicine, University of Washington, Box 359780, 325 Ninth Avenue, Seattle, WA 98109, USA.
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Schur
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000235:genetics* / Q000502:physiology*; D000328:Adult; D001823:Body Composition / Q000502:physiology; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000235:genetics; D050152:Intra-Abdominal Fat / Q000254:growth & development / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055815:Young Adult
keywords: DXA; Ectopic fat; Fat distribution; Zygosity