title: The challenge of a 2-year follow-up after intervention for weight loss in primary care.
abstract: BACKGROUND
  Many weight loss programmes show short-term success, but long-term data in larger studies are scarce, especially in community settings. Attrition is common and complicates the interpretation of long-term outcomes.
  
  
  OBJECTIVE
  To investigate 2-year outcomes and explore issues of attrition and missing data.
  
  
  METHODS
  A total of 772 overweight and obese adults recruited by primary care practices in Australia, Germany and the UK and randomised to a 12-month weight loss intervention delivered in a commercial programme (CP) or in standard care (SC).
  
  
  METHODS
  Weight change from 0-24 and 12-24 months including measured weights only and measured and self-reported weights, using last observation carried forward (LOCF), baseline observation carried forward (BOCF), completers-only and missing-at-random (MAR) analyses.
  
  
  RESULTS
  A total of 203 participants completed the 24-month visit. Using measured weights only, there was a trend for greater 24-month weight loss in CP than in SC, but the difference was only statistically significant in the LOCF and BOCF analyses: LOCF: -4.14 vs -1.99 kg, difference adjusted for centre -2.08 kg, P<0.001; BOCF: -1.33 vs -0.74 kg, adjusted difference -0.60 kg, P=0.032; completers: -4.76 vs -2.99 kg, adjusted difference -1.53 kg, P=0.113; missing at random: -3.00 vs -1.94 kg, adjusted difference -1.04 kg, P=0.150. Both groups gained weight from 12-24 months and weight regain was significantly (P<0.001) greater for CP than for SC in all analysis approaches. Inclusion of self-reported weights from a further 138 participants did not change the interpretation of the findings.
  
  
  CONCLUSIONS
  Initial weight loss was poorly maintained during the no-intervention follow-up, but both groups did have lower weight over the 24 months. Attrition was high in both groups, and assumptions about missing data had considerable impact on the magnitude and statistical significance of treatment effects. It is vital that trials on weight loss interventions consider the plausibility of these differences in an analytical approach when interpreting research findings and comparing data between studies.
authors.affiliation: Else Kroener-Fresenius-Centre for Nutritional Medicine, Technische Universität München, University Hospital 'Klinikum rechts der Isar', Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Holzapfel
authors.affiliation: MRC Biostatistics Unit, Cambridge, UK.
authors.forename: L
authors.initials: L
authors.lastname: Cresswell
authors.affiliation: MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.
authors.forename: A L
authors.initials: AL
authors.lastname: Ahern
authors.affiliation: Boden Institute, Medical Foundation Building K25, University of Sydney, Sydney, NSW, Australia.
authors.forename: N R
authors.initials: NR
authors.lastname: Fuller
authors.affiliation: MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.
authors.forename: M
authors.initials: M
authors.lastname: Eberhard
authors.affiliation: Else Kroener-Fresenius-Centre for Nutritional Medicine, Technische Universität München, University Hospital 'Klinikum rechts der Isar', Munich, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Stoll
authors.affiliation: MRC Biostatistics Unit, Cambridge, UK.
authors.forename: A P
authors.initials: AP
authors.lastname: Mander
authors.affiliation: MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK.
authors.forename: S A
authors.initials: SA
authors.lastname: Jebb
authors.affiliation: Boden Institute, Medical Foundation Building K25, University of Sydney, Sydney, NSW, Australia.
authors.forename: I D
authors.initials: ID
authors.lastname: Caterson
authors.affiliation: Else Kroener-Fresenius-Centre for Nutritional Medicine, Technische Universität München, University Hospital 'Klinikum rechts der Isar', Munich, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Hauner
mesh_terms: D000328:Adult; D001315:Australia / Q000453:epidemiology; D003625:Data Collection; D005260:Female; D005500:Follow-Up Studies; D005858:Germany / Q000453:epidemiology; D006801:Humans; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology / Q000517:prevention & control* / Q000523:psychology; D010349:Patient Compliance / Q000523:psychology / Q000706:statistics & numerical data; D011320:Primary Health Care; D016896:Treatment Outcome; D006113:United Kingdom / Q000453:epidemiology; D015430:Weight Gain; D015431:Weight Loss; D061217:Weight Reduction Programs
references.citation: Int J Obes Relat Metab Disord. 2001 Mar;25(3):325-31
references.pmid: 11319628
references.citation: Diabetes Obes Metab. 2008 Dec;10(12):1248-60
references.pmid: 18721258
references.citation: N Engl J Med. 2012 Oct 4;367(14):1355-60
references.pmid: 23034025
references.citation: N Engl J Med. 2011 Nov 24;365(21):1959-68
references.pmid: 22085317
references.citation: BMJ. 2011 Feb 07;342:d40
references.pmid: 21300711
references.citation: Lancet. 2012 Mar 17;379(9820):1003; author reply 1003
references.pmid: 22423881
references.citation: Behav Res Ther. 2010 Aug;48(8):706-13
references.pmid: 20691328
references.citation: Obes Rev. 2011 Nov;12(11):912-34
references.pmid: 21815990
references.citation: Lancet. 2011 Oct 22;378(9801):1485-92
references.pmid: 21906798
references.citation: Obes Rev. 2010 Dec;11(12):899-906
references.pmid: 20345430
references.citation: Obesity (Silver Spring). 2011 Oct;19(10):1987-98
references.pmid: 21779086
references.citation: N Engl J Med. 2011 Nov 24;365(21):1969-79
references.pmid: 22082239