In this quantitative review of 33 studies, we estimated that the annual direct medical cost of overweight is approximately $266 higher, and the incremental cost of obesity $1723 higher, than that of normal weight persons. These results were based on the four highest quality studies. Our pooled estimates (n = 33 studies) show per-person costs to be $498 (overweight) and $1630 (obesity). Based on our estimates of incremental cost from the four highest quality studies and using a recently published estimate of national health expenditures,65
the aggregate national cost of overweight and obesity was 4.8% of U.S. health spending in 2008, or 5.0% if pooled estimates are used. Estimates of the incremental cost of obesity were similar, whether only the highest quality studies were used or whether all studies were pooled. (The incremental cost of overweight was, in fact, lower for the highest quality studies.) Because the characteristics of high-quality studies were generally associated with larger cost estimates (), the finding of similar estimates in the pooled analysis and for the subset of high-quality studies was surprising. We believe that this result reflects the small number of high-quality studies.
We found substantial heterogeneity in costs among the studies. An important source of heterogeneity was study design (e.g., national samples versus health plan or employer samples). If only “nationally representative” studies had been used for this analysis, the aggregate national cost of overweight would be $48.2 billion and obesity would be $122 billion (i.e., $170.2 billion total, or 7.1% of health care spending in 2008). This latter estimate is closer to estimates from two recent studies that estimated current and future costs of obesity.15, 50
However, some national samples in the current analysis included only subpopulations by age, which led to a wide range of cost estimates.
Finkelstein et al, using recent Medical Expenditure Panel Survey data, reported that the incremental cost of obesity to be $1429 and that the cost of overweight was not significantly different than the cost of normal weight.15
Our cost estimate for obesity of $1723 is higher than Finkelstein’s, and we estimated a cost of $266 for overweight. We estimated that total spending was 4.8% of national expenditures, while Finkelstein estimated total spending to be 9.1%. The difference in percentage of health care spending occurs because Finkelstein et al used aggregate spending from the Medical Expenditure Panel Survey (MEPS) which is lower than aggregate spending from the National Health Expenditure Accounts (NHEA) which we used.65
Had we used MEPS aggregate expenditures, costs would be estimated at 10.4% (obesity alone) or 12.1% (obesity and overweight combined) of total health care spending. It is unclear whether aggregate spending from MEPS or from the NHEA is preferred. In another study, Wang and colleagues estimated future obesity-related health care costs for the U.S. health care system. They concluded that obesity-related expenditures would increase to 16–18% of health care spending by 2030. They also pointed out that the proportion of total health care expenditures attributable to obesity would be lower if MEPS was used and higher if NHEA was used.50
We did not attempt to project future obesity costs in this manuscript.
Another important source of variability in cost estimate was the age groups selected for analysis. The studies by Sturm et al and Daviglus et al were limited to near-elderly or elderly adults18, 26
and reported the incremental cost of obesity to be 2–3 times greater than the average that we calculated. Higher obesity-related health care spending for older age groups may reflect greater cumulative exposure to overweight/obesity (i.e., “pound-years”). The recent study by Wolf et al also reported large incremental costs.21
This study included spending for weight loss, a category not usually included in cost analyses.
A third important source of variability was BMI cutoff used. Some studies used non-standard definitions for obesity, in which BMI cutoffs were lower than the standard of 30 kg/m2
. This difference in classification, by including overweight individuals in the obese class, has the effect of lowering the incremental cost for both the overweight and obese groups.66
(Both means are lowered because those who are reclassified from overweight to obese represent the heaviest and most costly among overweight individuals, but their weight and cost is lower than that of the obese individuals with whom they are now classified.)
Several important limitations apply to this review. The most important limitation is the use of pooled analysis to summarize a heterogeneous group of studies. To overcome this limitation, we presented data from only four high-quality studies as the primary results. Second, although the review was quantitative, lack of variance estimates for cost precluded formal meta-analysis. Third, we were unable to adjust for some of the design decisions made by authors of the original reports. Fourth, we were not able to control for the type or number of medical conditions that individual studies counted as weight-related. For example, among the 4 attributable risk studies, the study that counted fewer medical diagnoses as obesity-related37
reported lower estimates of incremental cost. Lastly, the review does not provide information about the cost-effectiveness of weight loss programs or other interventions intended to reduce the direct medical cost of overweight and obesity.
Despite the limitations noted, our work has several implications. First, the results suggest that the financial burden of obesity is at least 2–3 times greater in the U.S. than in other developed countries. Obesity-related spending as a percentage of total health care spending is approximately 1–2.5% in Canada and in the European Union.67–70
The difference between the U.S. and the EU/Canada is likely a combination of higher obesity rates and higher per capita health care spending in the U.S. Higher obesity-related spending in the United States, a country that already has the largest expenditures in the world, provides support for those who advocate for greater attention to obesity prevention and treatment.71, 72
Second, as described above, our results indicate that study methodology potentially makes a large difference in estimates of cost. Third, although these results do not provide an estimate of cost-effectiveness for obesity treatment, they do provide data that can be used, together with economic analyses of interventions, to estimate how much of the cost of weight-related illness could be saved. For example, the sub-analysis examining the cost of morbid obesity (n = 5 studies) suggests that this subgroup incurs costs that are disproportionate to their numbers (i.e., 35% of the total cost of obesity, whereas morbidly obese individuals make up approximately 15% of all obese persons.62
) Disproportionately higher costs among the morbidly obese, in combination with studies showing that bariatric surgery can produce a return on investment (i.e., a cost savings),73, 74
suggests that surgical treatment of obesity, while costly, may be more cost-effective than lifestyle or pharmacologic treatment for the morbidly obese.
In conclusion, we found that a BMI ≥ 30 kg/m2 was associated with approximately $1723 of additional medical spending per year, while overweight (BMI 25 to 29.9 kg/m2) was associated with a more modest incremental cost of $266. Our review suggests that in the future, more accurate estimates of the cost of overweight and obesity will be obtained in studies that use nationally representative samples, report cost or expenditure, use standard BMI cutoffs, include all direct medical costs, and analyze adult subjects of all ages.