Supplementary Material for: Association between indicators of inequality and weight change following a behavioural weight loss intervention

Background: Weight loss through behavioural weight management interventions can have important health benefits for people with obesity. However, to maximise the health benefits, weight lost must be maintained. Evidence suggests that behavioural weight loss interventions do not exacerbate inequalities in the short-term. However, no study has yet considered whether inequalities exist in long-term weight change following intervention.

Aim: To investigate if there are inequalities in weight change following weight loss intervention.

Methods: We conducted a cohort analysis of data from the Weight Loss Referrals for Adults in Primary Care (WRAP) trial (N=1267). WRAP randomised participants to receive a brief intervention information booklet or vouchers for 12-weeks or 52-weeks of WW (formerly Weight Watchers) and followed them for 5-years. Multiple linear regression estimated the association between exposures (indicators of inequality) and outcome (change in weight between 1- and 5-years). Each model was adjusted for intervention group, baseline weight, weight change between baseline and 1-year, research centre, and source of the 5-year weight data.

Results: Of the 1267 participants in WRAP, 708 had weight change data available. Mean weight change between 1- and 5-years was +3.30 kg (SD 9.10 kg). A 1 year difference in age at baseline was associated with weight change of 0.11kg ((95%CI 0.06, 0.16), p<0.001). We did not find evidence of associations between ethnicity, gender, education, indices of multiple deprivation, household income, or other family members participating in a weight loss programme and weight change.

Conclusion: Except for age, we did not find evidence of inequalities in weight change following a behavioural intervention. Findings further support the use of behavioural weight management interventions as part of a systems wide approach to improving population health.