Body mass index and healthcare costs: a systematic literature review of individual participant data studies

Excess weight is associated with increased total healthcare costs, but it is less well known how the associations between excess weight and costs vary across different types of healthcare services. We reviewed studies estimating associations between body mass index and healthcare costs using individual participant data, and summarised how annual healthcare costs for overweight (BMI 25 to <30 kg/m2) and obese (≥30 kg/m2) individuals compared to those for healthy weight individuals (18.5 to <25 kg/m2). EMBASE and MEDLINE were searched from January 1990 to September 2016 and 75 studies were included in the review. Of these, 34 studies presented adequate information to contribute to a quantitative summary of results. Compared to individuals at healthy weight, the median increases in mean total annual healthcare costs were 12% for overweight and 36% for obese individuals. The percentage increases in costs were highest for medications (18% for overweight and 68% for obese), followed by inpatient care (12% and 34%), and ambulatory care (4% and 26%). Percentage increases in costs associated with excess weight were higher for women than men. The substantial costs associated with excess weight in different healthcare settings emphasise the need for investment to tackle this major public health problem.