title: Baseline characteristics associated with different BMI trajectories in weight loss trials: a case for better targeting of interventions.
abstract: OBJECTIVE
  Dietary weight loss interventions have heterogeneous outcomes in long-term studies, with many participants regaining part or all of the lost weight. Growth mixture modelling is a novel analytic approach that can be used to identify different trajectories of weight change during a trial rather than focussing on the total amount of weight lost.
  
  
  METHODS
  Data were pooled from two 12-month dietary weight loss studies where no significant difference was detected between the treatment and control arms, thus allowing analysis independent of treatment. The data set included 231 subjects (74.5% female), with a mean weight loss of 6.40 kg (4.96). Growth mixture models were used to identify participants with similar trajectories of change in body mass index (BMI).
  
  
  RESULTS
  Three subgroups were identified. A rapid and continuing BMI loss over the study period (rapid, n=53), a rapid initial weight loss in the first 3 months with a slowing rate over the remaining 9 months (maintainers, n=146) and those with an initial loss trajectory, which slowed and began to increase at 9 months (recidivists, n=53). Age (s.d.) and BMI (s.d.) were significantly different between the three groups (rapid 53 years (7), 28.99 kg/m(2) (3.30); maintainers 47 years (9), 30.90 kg/m(2) (2.95); recidivists 44 years (7), 34.84 kg/m(2) (1.92), both P<0.001).
  
  
  CONCLUSIONS
  Older subjects with lower BMIs were more likely to have a rapid and continuing weight loss in a 1-year dietary-based weight loss intervention. Different interventional approaches may be necessary for different ages and baseline BMIs and stratification prior to randomisation may be necessary to prevent confounding in weight loss trials.
authors.affiliation: National Institute for Applied Statistics Research Australia, School of Mathematics and Applied Statistics, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Batterham
authors.affiliation: School of Medicine/Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: L C
authors.initials: LC
authors.lastname: Tapsell
authors.affiliation: School of Medicine/Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales, Australia.
authors.forename: K E
authors.initials: KE
authors.lastname: Charlton
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D000068959:Body Weight Maintenance; D002986:Clinical Trials as Topic; D004038:Diet, Reducing / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D050177:Overweight / Q000178:diet therapy* / Q000503:physiopathology; D016896:Treatment Outcome; D015431:Weight Loss; D055815:Young Adult
references.citation: Am Stat. 2012;66(1):16-24
references.pmid: 23204562
references.citation: Alcohol Clin Exp Res. 2000 Jun;24(6):882-91
references.pmid: 10888079
references.citation: Psychol Methods. 2003 Sep;8(3):364-8; discussion 384-93
references.pmid: 14596496
references.citation: Value Health. 2013 Jan-Feb;16(1):164-76
references.pmid: 23337228
references.citation: Obesity (Silver Spring). 2012 Oct;20(10):2048-56
references.pmid: 22327053
references.citation: J Am Diet Assoc. 2007 Oct;107(10):1755-67
references.pmid: 17904936
references.citation: Obes Res. 1995 Sep;3 Suppl 2:211s-216s
references.pmid: 8581779
references.citation: Eur J Clin Nutr. 2014 Jul;68(7):778-85
references.pmid: 24667750
references.citation: J Biol Dyn. 2011 Nov;5(6):579-599
references.pmid: 24707319
references.citation: J Clin Epidemiol. 2014 Aug;67(8):947-51
references.pmid: 24774470
references.citation: Am J Clin Nutr. 2015 Mar;101(3):449-54
references.pmid: 25733628
references.citation: Ann Epidemiol. 2009 Oct;19(10):701-10
references.pmid: 19628410
references.citation: Psychol Methods. 2003 Sep;8(3):369-77; discussion 384-93
references.pmid: 14596497
references.citation: Lancet. 2014 Aug 30;384(9945):766-81
references.pmid: 24880830
references.citation: N Engl J Med. 2011 Oct 27;365(17):1597-604
references.pmid: 22029981
references.citation: Arq Bras Endocrinol Metabol. 2009 Mar;53(2):129-38
references.pmid: 19466204
references.citation: Int J Obes (Lond). 2011 Jun;35(6):785-92
references.pmid: 21042325
references.citation: Psychol Methods. 2003 Sep;8(3):338-63
references.pmid: 14596495
references.citation: Am J Clin Nutr. 2008 Oct;88(4):906-12
references.pmid: 18842775
references.citation: Obesity (Silver Spring). 2014 Jan;22(1):5-13
references.pmid: 24307184
references.citation: Obesity (Silver Spring). 2015 Jan;23(1):7-15
references.pmid: 25469998
references.citation: BMC Public Health. 2013 Dec 26;13:1231
references.pmid: 24369765
references.citation: Hum Hered. 2013;75(2-4):127-35
references.pmid: 24081228
references.citation: Am J Clin Nutr. 1982 Nov;36(5):936-42
references.pmid: 7137077