ABSTRACT Background: There is considerable heterogeneity in long-term weight-loss among people referred to obesity treatment programmes. It is unclear whether attendance to face to face sessions in the early weeks of the programme is an independent predictor of long-term success. Objective: To investigate whether frequency of attendance at a community weight-loss programme over the first 12 weeks is associated with long-term weight change. Methods: Participants were randomised to receive brief support only (control, n=211), or a weight-loss programme for 12-weeks (n=530) or 52-weeks (n=528). This study included participants with data on session attendance over the first 12 weeks (n=889), compared to the control group. The association between attendance (continuously) and weight loss was explored using a linear model. A multi-level mixed-effects linear model was used to investigate whether attendance (categorised as 0, 1, 2-5, 6-9 and 10-12 sessions) was associated with weight loss at 3, 12 and 24 months compared to the control. Results: For every session attended in the first 12 weeks, average weight loss was -0.259kg/session at 24 months (P=0.005). Analysis by attendance group found only those attending 10-12 sessions had significantly greater weight loss (-7.5kg [95%CI -8.1 to -6.9] at 12 months; -4.7kg [95%CI -5.3 to -4.1] at 24 months) compared to the control group (-3.4 [95%CI -4.5 to -2.4] at 12 months, -2.5 [95%CI -3.5 to -1.5] at 24 months). Early attendance was higher for people ≥70 years, but there was no evidence of a difference by gender, ethnicity, education or income. Conclusions: Greater attendance at a community weight-loss programme in the first 12 weeks is associated with enhanced weight-loss up to 24 months. Regular attendance at a programme could be used as a criterion for continued provision of weight-loss services to maximise the cost-effectiveness of interventions.

Key words: weight loss, attendance, commercial programme