The economic impact of obesity in the United States
Ross A Hammond
2010 Economic Studies Program, Brookings Institution, Washington DC, USA
Over the past several decades, obesity has grown into a major global epidemic. By 2002, nearly 500 million people were overweight worldwide. In the United States (US), rates of obesity have doubled since 1970 to over 30%, with more than two-thirds of Americans now overweight. The determinants of this epidemic are likely complex,2,3 with substantial heterogeneity at the individual level in both causes and consequences that is beyond the scope of the current review. In this article, we provide an overview of the state of research on the likely economic impact of the US obesity epidemic at the aggregate level. We conducted a broad search of the literature that addresses potential economic costs of obesity. The most recent studies that sample US populations have identiﬁed at least four major
categories of economic impact linked with the obesity epidemic: direct medical costs, productivity costs, transportation costs, and human capital costs. We systematically review current evidence on each set of costs in turn, and discuss important gaps for future research along with potential trends in future economic impacts of obesity. This review adds to the current research on the economic impact of obesity by providing a more comprehensive overview of the range of effects, as well as a summary of the most up-to-date estimates.
Direct medical costs
One of the most cited economic impacts of the obesity epidemic is on direct medical spending. Obesity is linked with higher risk for several serious health conditions, Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy such as hypertension, type 2 diabetes, hypercholesterolemia, coronary heart disease (CHD), stroke, asthma, and arthritis. Direct medical spending on diagnosis and treatment of these conditions, therefore, is likely to increase with rising obesity
levels. Several studies offer retrospective or prospective estimates of the degree of disease incidence that can be linked to obesity, and of the magnitude of associated direct medical costs.
Incidence of diseases associated with obesity
The most common deﬁnitions of obesity are based on body mass index (BMI), deﬁned as weight in kilograms divided by height in meters squared. Obesity in adults is generally deﬁned as a BMI of 30.0 or greater, with BMI of 25.0–29.9 categorized as overweight. Thompson et al present a dynamic model of the relationships between BMI and the risks of ﬁve diseases linked with obesity: hypertension, hypercholesterolemia, type 2 diabetes mellitus, CHD, and stroke. The model captures both direct and indirect effects of obesity on health outcomes – obesity is a risk factor for hypertension, hypercholesterolemia, and diabetes, which are themselves risk factors for CHD and stroke. Estimated using a variety of data sources (including the National Health And Nutritional Examination Survey or NHANES, and the Framingham Study), the model gives future risks of all ﬁve diseases, life expectancy, and lifetime medical costs associated with the ﬁve diseases for men and women aged 35 to 64 years in each of four representative BMI groups (“healthy” BMI of 22.5, “overweight” BMI of 27.5, “obese” BMI of 32.5, and “severely obese” BMI of 37.5). BMI is assumed to be constant at its initial value for all individuals, with other risk factors adjusted for each year of aging. Results from the model demonstrate substantial increases in disease risk with increasing BMI. Relative to the group with BMI of 22.5, risk of hypertension is 40%–60% higher in the overweight (BMI 27.5), and twofold higher in the obese (BMI 32.5). Lifetime risk of CHD is 41.8% in obese men compared to 34.9% in the nonobese; for women, risk increases from 25% for the nonobese to 32.4% for the obese.
Similar relative disease risk rates for the overweight and obese are found in large-scale population studies. The Health Professionals Follow-up Study, based on 29,000 men observed over a three year time-period, found CHD risk to be 50% higher in the overweight (BMI 25–28.9), twice as high in the obese (BMI 29–32.9), and three times as high in the severely obese (BMI 33), compared to healthy weight men (BMI 23).6 for women, analysis based on the Nurses Health Study found the relative risk of type 2 diabetes to be 40.3 for women with BMIs between 31 and 32.9 (compared to those with BMI of less than 22). Analysis of NHANES-II
cross-sectional data for both men and women found risk of hypertension and diabetes to be increased 3.0 times and 2.9 times, respectively, compared to the nonoverweight. A large-scale telephone survey of 195,000 adults11 found the odds ratio for the overweight and obese (compared to normal weight) to be 1.59 and 3.44, respectively for diabetes, 1.82 and 3.50, respectively for high blood pressure, and 1.50 and 1.91, respectively for high cholesterol. Statistically signiﬁcant
effects for asthma and arthritis were also found. A different study quantiﬁed an increase of 1 mmHg in systolic blood pressure resulting from each one-unit increase in BMI among healthy 20–29 year olds.