Effectiveness of a once per week delivery of a family-based childhood obesity intervention: a cluster randomised controlled trial

Background: The effectiveness of once per week (OPW) delivery of a family-based childhood obesity programme was compared with twice per week (TPW) delivery in achieving health and behavioural outcomes at a population level and in improving programme attendance. Both programmes were delivered over 10-weeks, and the contact hours in the OPW and TPW programmes were 20 and 35-h, respectively. Methods: A cluster-randomised controlled trial with stratification by local health district was conducted. Height, weight and global self esteem of participants and parent-reported diet and physical activity were measured at programme commencement and completion and at 6-month follow-up. Attendance was defined as the proportion of total sessions attended. Results: There were no differences between the OPW and TPW arms in changes from pre-programme baseline for body mass index (BMI) z-score and other health and behaviourial measures at programme completion and at follow-up, except for the increase in physical activity outside of the programme at programme completion (OPW, 3.5 h/week; TPW, 1.9 h/week; p=0.03). OPW and TPW participants attended 71.2% and 69.2% of the total sessions, respectively. Attendance was the only contributing factor to a positive BMI z-score outcome (beta = -2.45, p<0.01) with no effects of child age and gender, language spoken at home or highest qualification of mother. Conclusions: A family-based childhood obesity programme can be delivered OPW with no compromise to health or behavioural outcomes compared with TPW. Higher attendance, as a proportion of available sessions, leads to better outcomes for children.