title: Improved eating behaviours mediate weight gain prevention of young adults: moderation and mediation results of a randomised controlled trial of TXT2BFiT, mHealth program.
abstract: BACKGROUND
  Explanatory evaluation of interventions for prevention of weight gain is required beyond changes in weight, to determine for whom the intervention works and the underlying mechanisms of change. It was hypothesised that participant characteristics moderate intervention effect on weight change and improved eating and physical activity behaviours during the 3-month program mediate the relationship between intervention and weight.
  
  
  METHODS
  In our randomised controlled trial, young adults at risk of weight gain (n = 250) were assigned either to an intervention group that received a 3-month mHealth (TXT2BFiT) program with 6-month maintenance or to a control group. Data were collected via online self-report surveys. Hypothesised moderators and mediators of the intervention effect on weight were independently assessed in PROCESS macro models for 3 and 9-month weight change.
  
  
  RESULTS
  Males (P = 0.01), mid-20s age group (P = 0.04), and higher income earners (P = 0.02) moderated intervention effects on weight change at 3-months and males only at 9-months (P = 0.02). Weight change at 3 (-1.12 kg) and 9-months (-1.38 kg) remained significant when 3-month nutrition and physical activity behaviours were specified as mediators (P <0.01 and P = 0.01 respectively). Indirect paths explained 39% (0.72/1.85 kg) and 40 % (0.92/2.3 kg) of total effect on weight change at 3 and 9-months respectively. Increased vegetable intake by intervention group at 3-months accounted for 19 and 17% and decreased sugar-sweetened beverages accounted for 8 and 13% of indirect weight change effects at 3 and 9-months respectively.
  
  
  CONCLUSIONS
  TXT2BFiT was effective for both young men and women. Small sustained behavioural changes, including increased vegetable intake and decreased sugar-sweetened beverages consumption significantly mediated the intervention's effects on weight change. Improved eating behaviours and increased physical activity accounted for approximately 40% of the weight change.
  
  
  BACKGROUND
  The trial is registered with the Australian New Zealand Clinical Trials Registry ( ACTRN12612000924853 ).
authors.affiliation: School of Life and Environmental Sciences, Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia. stephanie.partridge@sydney.edu.au.
authors.forename: Stephanie R
authors.initials: SR
authors.lastname: Partridge
authors.affiliation: Sydney School of Public Health, Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Kevin
authors.initials: K
authors.lastname: McGeechan
authors.affiliation: Sydney School of Public Health, Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Adrian
authors.initials: A
authors.lastname: Bauman
authors.affiliation: Sydney School of Public Health, Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Philayrath
authors.initials: P
authors.lastname: Phongsavan
authors.affiliation: School of Life and Environmental Sciences, Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Allman-Farinelli
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia; D001628:Beverages; D001835:Body Weight; D000068959:Body Weight Maintenance; D004032:Diet; D019422:Dietary Sucrose / Q000008:administration & dosage; D015444:Exercise; D005247:Feeding Behavior; D005260:Female; D006293:Health Promotion; D006801:Humans; D008297:Male; D009520:New Zealand; D009765:Obesity / Q000517:prevention & control*; D015397:Program Evaluation; D057566:Self Report; D013549:Sweetening Agents; D017216:Telemedicine; D060145:Text Messaging; D015430:Weight Gain; D055815:Young Adult
chemical_list: D019422:Dietary Sucrose; D013549:Sweetening Agents
keywords: Lifestyle; Mediation; Moderation; Nutrition; Obesity prevention; Young adults; mHealth