title: Does the amount of fat mass predict age-related loss of lean mass, muscle strength, and muscle quality in older adults?
abstract: BACKGROUND
  An excessive amount of adipose tissue may contribute to sarcopenia and may be one mechanism underlying accelerated loss of muscle mass and strength with aging. We therefore examined the association of baseline total body fat with changes in leg lean mass, muscle strength, and muscle quality over 7 years of follow-up and whether this link was explained by adipocytokines and insulin resistance.
  
  
  METHODS
  Data were from 2,307 men and women, aged 70-79 years, participating in the Health, Aging, and Body Composition study. Total fat mass was acquired from dual energy X-ray absorptiometry. Leg lean mass was assessed by dual energy X-ray absorptiometry in Years 1, 2, 3, 4, 5, 6, and 8. Knee extension strength was measured by isokinetic dynamometer in Years 1, 2, 4, 6, and 8. Muscle quality was calculated as muscle strength divided by leg lean mass.
  
  
  RESULTS
  Every SD greater fat mass was related to 1.3 kg more leg lean mass at baseline in men and 1.5 kg in women (p < .01). Greater fat mass was also associated with a greater decline in leg lean mass in both men and women (0.02 kg/year, p < .01), which was not explained by higher levels of adipocytokines and insulin resistance. Larger fat mass was related to significantly greater muscle strength but significantly lower muscle quality at baseline (p < .01). No significant differences in decline of muscle strength and quality were found.
  
  
  CONCLUSIONS
  High fatness was associated with lower muscle quality, and it predicts accelerated loss of lean mass. Prevention of greater fatness in old age may decrease the loss of lean mass and maintain muscle quality and thereby reducing disability and mobility impairments.
authors.affiliation: National Institute on Aging, 7201 Wisconsin Avenue, Bethesda, MD 20892, USA. a.koster@maastrichtuniversity.nl
authors.forename: Annemarie
authors.initials: A
authors.lastname: Koster
authors.forename: Jingzhong
authors.initials: J
authors.lastname: Ding
authors.forename: Sari
authors.initials: S
authors.lastname: Stenholm
authors.forename: Paolo
authors.initials: P
authors.lastname: Caserotti
authors.forename: Denise K
authors.initials: DK
authors.lastname: Houston
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Nicklas
authors.forename: Tongjian
authors.initials: T
authors.lastname: You
authors.forename: Jung Sun
authors.initials: JS
authors.lastname: Lee
authors.forename: Marjolein
authors.initials: M
authors.lastname: Visser
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.forename: Ann V
authors.initials: AV
authors.lastname: Schwartz
authors.forename: Jane A
authors.initials: JA
authors.lastname: Cauley
authors.forename: Frances A
authors.initials: FA
authors.lastname: Tylavsky
authors.forename: Bret H
authors.initials: BH
authors.lastname: Goodpaster
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Kritchevsky
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data; D000273:Adipose Tissue / Q000033:anatomy & histology*; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001132:Arm / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D015331:Cohort Studies; D004215:Distance Perception; D005260:Female; D006801:Humans; D015994:Incidence; D007600:Judgment; D008297:Male; D009043:Motor Activity; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009929:Organ Size; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011597:Psychomotor Performance / Q000502:physiology; D013851:Thinness