title: Slimming World in Stop Smoking Services (SWISSS): study protocol for a randomized controlled trial.
abstract: BACKGROUND
  Quitting smokers gain weight. This deters some from trying to stop smoking and may explain the increased incidence of type 2 diabetes after cessation. Dieting when stopping smoking may be counterproductive. Hunger increases cravings for smoking and tackling two behaviours together may undermine quitting success. A meta-analysis of randomized controlled trials (RCTs) showed individualized dietary support may prevent weight gain, although there is insufficient evidence whether it undermines smoking cessation. Commercial weight management providers (CWMPs), such as Slimming World, provide individualized dietary support for National Health Service (NHS) patients; however, there is no evidence that they can prevent cessation-related weight gain.Our objective is to determine whether attending Slimming World from quit date, through referral from NHS Stop Smoking Services, is more effective than usual care at preventing cessation-related weight gain.
  
  
  METHODS
  This RCT will examine the effectiveness of usual cessation support plus referral to Slimming World compared to usual cessation support alone. Healthy weight, overweight and obese adult smokers attending Stop Smoking Services will be included. The primary outcome is weight change in quitters 12 weeks post-randomization. Multivariable linear regression analysis will compare weight change between trial arms and adjust for known predictors of cessation-related weight gain.We will recruit 320 participants, with 160 participants in each arm. An alpha error rate of 5% and 90% power will detect a 2 kg (SD = 2.5) difference in weight gain at 12 weeks, assuming 20% remain abstinent by then.
  
  
  CONCLUSIONS
  This trial will establish whether referral to the 12-week Slimming World programme plus usual care is an effective intervention to prevent cessation-related weight gain. If so, we will seek to establish whether weight control comes at the expense of a successful quit attempt in a further non-inferiority trial.Positive results from both these trials would provide a potential solution to cessation-related weight gain, which could be rolled out across England within Stop Smoking Services to better meet the needs of 0.75 million smokers stopping with NHS support every year.
  
  
  BACKGROUND
  Current Controlled Trials ISRCTN65705512.
authors.affiliation: Department of Health Professions, Faculty of Health and Life Sciences RC131, Coventry University, Priory Street, Coventry CV1 5FB, UK. deborah.lycett@coventry.ac.uk
authors.forename: Deborah
authors.initials: D
authors.lastname: Lycett
authors.forename: Paul
authors.initials: P
authors.lastname: Aveyard
authors.forename: Andrew
authors.initials: A
authors.lastname: Farmer
authors.forename: Amanda
authors.initials: A
authors.lastname: Lewis
authors.forename: Marcus
authors.initials: M
authors.lastname: Munafò
mesh_terms: D002985:Clinical Protocols; D004032:Diet / Q000009:adverse effects; D004739:England; D015444:Exercise; D006801:Humans; D016014:Linear Models; D015999:Multivariate Analysis; D012017:Referral and Consultation; D012107:Research Design; D040242:Risk Reduction Behavior; D012907:Smoking / Q000523:psychology; D016540:Smoking Cessation / Q000379:methods*; D000074606:Smoking Prevention; D013222:State Medicine; D013997:Time Factors; D016896:Treatment Outcome; D015430:Weight Gain; D015431:Weight Loss; D061217:Weight Reduction Programs