title: BMI, body composition, and physical functioning in older adults.
abstract: OBJECTIVE
  Recent studies have emphasized the importance of muscle and fat mass in relation to age-related decline in physical function. Our objective was to determine whether BMI, as a surrogate measurement of fat mass, may be used as a measure of risk factor for physical functioning in older adults and whether body composition measurements confer any advantage over BMI.
  
  
  METHODS
  Four thousand men and women>or=65 years of age living in the community, stratified by age and sex, underwent the following measurements: body composition by DXA; grip strength; and timed 6-m walk. Subjects were grouped into five categories of BMI using Asian criteria for health-related risks, and between-group differences in physical performance measures and body composition were analyzed using analysis of covariance adjusting for age, physical activity level, and presence of chronic disease.
  
  
  RESULTS
  Subjects in the two obese categories had a significantly greater number of instrumental activities of daily living (IADL) impairments compared with the underweight and normal-weight groups. Those with BMI>or=30 kg/m2 had the worst walking performance, and the groups with BMI in the normal and overweight range had optimal performance. Fat mass, but not appendicular muscle mass, was associated with walking speed after adjusting for BMI.
  
  
  CONCLUSIONS
  Fat mass seems to be a more important factor than appendicular muscle mass in determining walking speed in community-living older adults, even after adjusting for BMI.
authors.affiliation: Department of Medicine and Therapeutics, Jockey Club Osteoporosis Centre, Faculty of Medicine, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, N.T. Hong Kong. jeanwoowong@cuhk.edu.hk
authors.forename: Jean
authors.initials: J
authors.lastname: Woo
authors.forename: Jason
authors.initials: J
authors.lastname: Leung
authors.forename: Timothy
authors.initials: T
authors.lastname: Kwok
mesh_terms: D000203:Activities of Daily Living; D000273:Adipose Tissue / Q000033:anatomy & histology; D000368:Aged; D000704:Analysis of Variance; D001823:Body Composition; D015992:Body Mass Index; D002908:Chronic Disease; D005260:Female; D006723:Hong Kong; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D009765:Obesity / Q000453:epidemiology / Q000503:physiopathology; D010809:Physical Fitness; D016138:Walking / Q000502:physiology