Randomization
Following baseline data collection, eligible and consented participants were randomized on a 1:1 ratio to either the RUFIT-NZ intervention or the control group using a computerized randomization process that ensured allocation concealment. Randomization was stratified by baseline BMI category (< 35 kg/m2 versus ≥ 35 kg/m2), self-reported ethnicity (Māori, Pasifika, non-Māori/non-Pasifika), and study center, using stratified block randomization with variable block sizes of two or four. The randomization sequence was generated by our biostatistician (YJ). Participants were informed by email of their eligibility and allocation group within 2–3 days of their baseline assessment at the club. Due to the nature of the study, participants and research assistants were aware of the treatment allocation post-randomization. Study investigators and the trial statistician were blinded during analysis. To reduce assessment bias, objective measures of height and weight were collected by trained researchers at 12- and 52-weeks.