title: Relationships among fat mass, fat-free mass and height in adults: A new method of statistical analysis applied to NHANES data.
abstract: OBJECTIVE
  The positive influence of fat mass (FM) on fat-free mass (FFM) has been quantified previously by various methods involving regression analysis of population data, but some are fundamentally flawed through neglect of the tendency of taller individuals to carry more fat. Differences in FFM due to differences in FM-and not directly related to differences in height-are expressed as ΔFFM/ΔFM, denoted KF. The main aims were to find a sounder regression-based method of quantifying KFand simultaneously of estimating mean BMI0, the BMI of hypothetical fat-free individuals. Other, related, objectives were to check the linearity of FFM-FM relationships and to quantify the correlation between FM and height.
  
  
  METHODS
  New statistical methods, explored and verified by Monte Carlo simulation, were applied to NHANES data. Regression of height2on FFM and FM produced estimates of mean KFand indirectly of BMI0. Both were then adjusted to allow for variability in KFaround its mean. Its standard deviation was estimated by a novel method.
  
  
  RESULTS
  Relationships between FFM and FM were linear, not semilogarithmic as is sometimes assumed. Mean KFis similar in Mexican American men and women, but higher in men than women in non-Hispanic European Americans and African Americans. Mean BMI0is higher in men than in women. FM correlates more strongly with height than has been found previously.
  
  
  CONCLUSIONS
  A more accurate way of quantifying mean BMI0and the dependence of FFM on FM is established that may be easily applied to new and existing population data.
authors.affiliation: School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom.
authors.forename: Richard F
authors.initials: RF
authors.lastname: Burton
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D000886:Anthropometry / Q000379:methods*; D001827:Body Height; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009749:Nutrition Surveys; D012044:Regression Analysis; D014481:United States; D055815:Young Adult