Abstract Background This study aimed to estimate annual health care and lost productivity costs associated with excess weight among the adult population in Belgium, using national health data. Methods Health care costs and costs of absenteeism were estimated using data from the Belgian national health interview survey (BHIS) 2013 linked with individual health insurance data (2013–2017). Average yearly health care costs and costs of absenteeism were assessed by body mass index (BMI) categories – i.e., underweight (BMI