Objective Health-care access is associated with improved control of multiple chronic diseases, but the association between health-care access and weight change is unclear. The present study aims to test the association between health-care access and weight change. Design The Coronary Artery Risk Development in Young Adults (CARDIA) Study is a multicentre population-based prospective study. Weight change was calculated at 3 and 13 years after CARDIA year 7 (1992-1993). Health-care access was defined as no barriers or one or more barriers to access (health insurance gap, no usual source of care, not seeking care due to expense). Intermediary variables evaluated included history of dieting and use of diet pills, meal replacements or weight-control programmes. Setting Four cities in the USA. Subjects Participants were aged 18-30 years at baseline (1985-1986). Analyses include 3922 black and white men and women with relevant data from CARDIA years 7, 10 and 20 (1992-1993, 1995-1996 and 2005-2006, respectively). Results Mean weight change was +2·22 kg (+4·9 lb) by 3 years and +8·48 kg (+18·7 lb) by 13 years, with no differences by health-care access. Being on a weight-reducing diet was not consistently associated with health-care access across examinations. Use of diet pills, meal replacements or organized weight-control programmes was low, and did not vary by health-care access. Conclusions Weight gain was high irrespective of health-care access. Public health and clinical approaches are needed to address weight gain. © The Authors 2012.