title: Clinical measures of adiposity and percentage fat loss: which measure most accurately reflects fat loss and what should we aim for?
abstract: OBJECTIVE
  To determine which clinical measure of childhood obesity should be monitored to best reflect change in adiposity in a weight management programme and estimate the degree of change needed to be relatively certain of fat reduction.
  
  
  METHODS
  92 obese children with a mean (range) age of 12.8 (6.9-18.9) years and a mean body mass index standard deviation score (BMI SDS) of +3.38 (+2.27 to +4.47) attending a hospital-based clinic on a regular, 3 monthly basis.
  
  
  METHODS
  Pairs of weight and height measured up to 2.41 years apart used to derive BMI as kg/m2, and adjusted for age and gender to give weight and BMI SDS (BMI-z score) using British 1990 Growth Reference Data. Contemporaneous adiposity estimated by fatness measured by a bioimpedance segmental body composition analyser.
  
  
  RESULTS
  Changes in BMI-z scores, compared to BMI, weight and weight SDS, most accurately reflected loss of fat. Reductions of 0.25, 0.5, 0.75, and 1 BMI SDS equate to expected mean falls in total body fat percentage of 2.9%, 5.8%, 8.7% and 11.6%. Approximate 95% prediction intervals indicated that a fall in BMI SDS of at least 0.6 over 6-12 months (or 0.5 over 0-6 months) is consistent with actual fat loss.
  
  
  CONCLUSIONS
  Change in BMI-z score best reflects percentage fat loss compared to BMI, weight and weight SDS. The wide variation in likely percentage fat loss for a given BMI SDS reduction means a loss of 0.5-0.6 is required to be relatively certain of definite percentage fat reduction.
authors.affiliation: Department of Endocrinology, Diabetes and Metabolism, Bristol Royal Hospital for Children and University of Bristol, Bristol, UK.
authors.forename: Linda P
authors.initials: LP
authors.lastname: Hunt
authors.forename: Anna
authors.initials: A
authors.lastname: Ford
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Sabin
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Crowne
authors.forename: Julian P H
authors.initials: JP
authors.lastname: Shield
mesh_terms: D000273:Adipose Tissue / Q000473:pathology; D050154:Adiposity; D000293:Adolescent; D000886:Anthropometry; D001499:Bayes Theorem; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D009765:Obesity / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D010992:Plethysmography, Impedance; D016896:Treatment Outcome; D015431:Weight Loss