Background: Almost one-third of adult Canadians are at increased risk of disability, disease and premature death because of being obese. In order to allocate limited health care resources rationally, it is necessary to elucidate the economic burden of obesity.

Objective: To estimate the direct costs related to the treatment of and research into obesity in Canada in 1997.

Methods: The prevalence of obesity (body mass index of 27 or greater) in Canada was determined using data from the National Population Health Survey, 1994-1995. Ten comorbidities of obesity were identified from the medical literature. A population attributable fraction (PAF) was calculated for each comorbidity with data from large cohort studies to determine the extent to which each comorbidity and its management costs were attributable to obesity. The direct cost of each comorbidity was determined using data from the Canadian Institute of Health Information (for direct expenditure categories) and from Health Canada (for the proportion of expenditure category attributable to the comorbidity). This prevalence-based approach identified the direct costs of hospital care, physician services, services of other health professionals, drugs, other health care and health research. For each comorbidity, the cost attributable to obesity was determined by multiplying the PAF by the total direct cost of the comorbidity. The overall impact of obesity was estimated as the sum of the PAF-weighted costs of treating the comorbidities. A sensitivity analysis was completed on both the estimated costs and the PAFs.

Results: The total direct cost of obesity in Canada in 1997 was estimated to be over $1.8 billion. This corresponded to 2.4% of the total health care expenditures for all diseases in Canada in 1997. The sensitivity analysis revealed that the total cost could be as high as $3.5 billion or as low as $829.4 million; this corresponded to 4.6% and 1.1% respectively of the total health care expenditures in 1997. When the contributions of the comorbidities to the total cost were considered, the 3 largest contributors were hypertension ($656.6 million), type 2 diabetes mellitus ($423.2 million) and coronary artery disease ($346.0 million).

Interpretation: A considerable proportion of health care dollars is devoted to the treatment and management of obesity-related comorbidities in Canada. Further research into the therapeutic benefits and cost-effectiveness of management strategies for obesity is required. It is anticipated that the prevention and treatment of obesity will have major positive effects on the overall cost of health care.