Inactivity is a major cause of impaired glucose tolerance and contributes to poor energy balance (obesity guidelines). In cultures with abundant energy intake, lack of physical activity contributes to the development of obesity—or weight gain—as a consequence of excess energy intake beyond energy expenditure. Inactivity is related to increased risk of cardiovascular disease (CVD) (1). Cardiovascular disease is the leading cause of death in the United States. Approximately 58 million persons in the United States (20% of the total population) have one or more types of CVD (29). These types of CVD include: high blood pressure, CHD, stroke, rheumatic heart disease, and other forms of heart disease. Behavioral risk factors for CVD include physical inactivity and being overweight. In 1994 CVD accounted for 45.2% of all deaths in the United States.
Other major morbidity caused by inactivity includes colon cancer (7), osteoporosis and particularly hip fracture (18), and Type II diabetes (47). Higher levels of activity may reduce risk of breast cancer, although the magnitude of this relation remains uncertain (12). In each of these major medical conditions the adverse effect of inactivity is independent of body weight or adiposity. As a consequence of this independence, the burden of inactivity can be added to that attributable to obesity.
Overweight and obesity are major risk factors for many chronic diseases and also exacerbate many chronic conditions, including hypertension, high cholesterol, and osteoarthritis (34,46). Men and women at even modest levels of adiposity are at increased risk of morbidity. Further, adult weight gain is related to increased risk of coronary heart disease (CHD) (40,48), non-insulin-dependent or Type II diabetes mellitus (4,8), postmenopausal breast cancer (20), and mortality (26).
To address the full impact of behaviors such as inactivity and excess weight on health and their consequences, one can summarize the burden of premature mortality. McGinnis and Foege (28) estimate that lack of activity and diet contribute to 14% of mortality. Hahn et al. (17) estimate that sedentary lifestyle contributes to 23% of deaths from the leading chronic diseases. Data from the follow-up of the Iowa Women’s Health Study (23) indicate a strong inverse relation between physical activity and total mortality among women, and the Harvard Alumni study shows a similar relationship among men (36).
Although mortality is commonly used as a measure of disease burden, it does not account for the morbidity associated with chronic conditions. Further, it omits any accounting of the impact of lifestyle on health-related quality of life. One can use an economic measure to summarize this broad range of health effects. Such a measure can account for both nonfatal and fatal conditions.
The direct costs of illness include the costs of diagnosis and treatment related to any disease (hospital stay, nursing home, medications, physician visits). The value of lost productivity is an indirect cost of illness. This includes wages lost by people unable to work because of disease and also the forgone wages resulting from premature mortality. These future earnings after death are translated into current monetary value using an inflation or discount factor, usually 3%. We do not quantify these costs in the current analysis.
Approximately 60 million U.S. adults are overweight, one-third of the population (10,32). Further, the prevalence of overweight and obesity has been increasing (10). The age-adjusted prevalence of obesity increased by 30% from 1980 to 1994 (22). The proportion of the U.S. adult population aged > 20-yr old exceeding the healthy weight ranges (that is the prevalence of BMI> 25.0) is high; 59.4% of men, 50.7% of women, or 54.9% of the total U.S. population. Overall 22.8% of the adult population, 24.8% of women and 20% of men, are obese (BMI >30).
Despite its benefits, many people do not engage in regular physical activity. The Behavioral Risk Factor Surveillance System (BRFSS) reported that in 1995 approximately 28.8% of the U.S. adult population reported no leisure-time physical activity (30). In some states up to 48% reported no leisure-time physical activity.
METHODS
We searched the MEDLINE database for studies reporting the economic costs of obesity or inactivity, or cost of illness. From the identified references, those relating to obesity or conditions attributable to obesity were reviewed. As estimates of the cost of obesity have been reported more than once for several countries, the most up-to-date estimates were extracted.
To estimate the proportion of disease that could be prevented by eliminating inactivity or obesity we calculate the population-attributable risk percent. This is the maximum proportion of disease attributable to the specific exposure (obesity or lack of physical activity). PAR% is based on the incidence of disease in the exposed (i.e., inactive group) as compared with the nonexposed, taking relative risks from analyses that control for confounders (e.g., age, smoking, dietary intake, etc.). PAR% is calculated using P(RR-1)/1 +P (rr-1), where P is the prevalence of exposure in the population and RR the relative risk for disease.
The procedures to estimate the costs of diabetes and gallstones are presented elsewhere (6,21). Annual direct costs of hypertension and CHD were extrapolated from Hodgson and Kopstein (19). All costs are inflated to 1995 dollars using the medical component of the consumer price index.
RESULTS
Cost attributable to inactivity.
Using the prevalence of inactivity as 28.8% (the median prevalence for U.S. adults reporting no leisure-time physical activity in 1995), we conservatively estimate the PAR% for inactivity and multiply this by the annual costs of illness caused by lack of physical activity. We estimate that 22% of CHD, 22% of colon cancer, 22% of osteoporotic fractures, 12% of diabetes and hypertension, and perhaps 5% of breast cancer are attributable to lack of physical activity (see Table 1).
;)
Table 1: Costs of inactivity (billion $), in the United States, 1995.
Overall, sedentary behavior and lack of physical activity costs the U.S. a conservative total of 24.3 billion dollars per year for direct health care delivery costs. That is, approximately 2.4% of all health care costs in 1995 are due to or are the result of lack of physical activity.
In a sensitivity analysis we estimate the costs resulting from inactivity using the upper bound of state level reports of no physical activity (48%). This may more closely approximate the proportion of the population with insufficient activity to avoid the health consequences of inactivity. Using this prevalence and retaining the relative risk for the association between activity and the major health outcomes we estimate the costs of inactivity as 37.2 billion dollars (3.7% of direct health care costs).
Costs of obesity.
The direct costs of obesity have been estimated for several countries. Because the majority of identified studies follow the methods reported by Colditz in 1992, this approach is described here (6). The prevalence-based estimate of the burden of obesity is based on the disease prevalence and the estimated proportion of disease attributable to obesity. Diseases considered included non-insulin-dependent diabetes mellitus (NIDDM), gall bladder disease, cardiovascular disease, cancer (colon and prostate in men; breast, endometrium, cervix, and ovarian in women). This analysis used a definition of obesity as BMI greater than 27.8 for men and 27.3 for women. Subsequent analyses have approximated the current recommended definition of obesity at BMI of 30.
Using a prevalence-based approach to estimate the costs of obesity in the United States, Wolf and Colditz (49) estimate the proportion of disease attributable to obesity and the associated costs. Conditions included in their analysis were Type II diabetes, CHD, hypertension, gallbladder disease, postmenopausal breast cancer, endometrial cancer, colon cancer, and osteoarthritis. Using prevalences from the National Health and Nutrition Examination Survey III (NHANES III) (22.4% overall and 24.9% for breast and endometrial cancers) we update the costs attributable to obesity. Overall the direct health care costs of obesity were approximately 70 billion dollars or 7% of total health care cost (see Table 2).
Table 2: Costs ($ billions) of obesity (BMI > 30) in the United States, 1995.
Costs of obesity in other countries.
Using this same approach as Colditz, Levy (24) estimated that the costs of obesity in France was approximately 2% in 1992 (Table 3). In The Netherlands, Seidell estimates that the cost is 4% of the national health care costs (44), and Segal estimates that for Australia obesity is responsible for 2% of the costs of health care (43). The definition of obesity, the conditions included in cost estimates, and the findings from these studies are summarized in Table 3.
Table 3: Cost of obesity from different countries.
We have previously reported the economic costs of obesity for the United States using overweight defined as body mass index greater than 27 kg·m−2. Now, with the World Health Organization definition of obesity as moderate obesity for BMI 25–29.9, severe overweight as BMI 30–39.9, and massive obesity as BMI 40 or more, we conservatively estimate the economic impact of obesity for BMI greater than 29 (49). It is clear that this underestimates the total costs of obesity, in part because we omit the costs for illness among those who are overweight (BMI 25–29.9). In addition, we omit several conditions related to obesity. These include benign prostatic hypertrophy which is related to increased abdominal adiposity (14) and lack of activity (37) and infertility (J. W. Richards et al., personal communication). Asthma may also be increased by obesity.
Indirect costs.
Early retirement and increased risk of disability pensions together add indirect costs that are not included in the estimates for individual countries summarized above. Narbro et al. (31) estimate that for Sweden, obese subjects are 1.5–1.9 times more likely to take sick leave and that 12% of obese women had disability pensions attributable to obesity, costing some 300 million U.S. dollars for 1 million in the female adult population. Overall approximately 10% of sick leave and disability pensions in women may be related to obesity and obesity related conditions (31). Discrimination against those who are obese may lead to poor quality of life and downward social mobility (42).
The indirect costs attributable to obesity amount to at least 48 billion dollars. The major contributor to these costs is CHD (48%), which accounts for the large portion of premature mortality. Other indirect costs were NIDDM (17.5%), and osteoarthritis (17.1%); the latter largely resulted from excess bed days, work days lost, and restricted activity days.
Total direct costs of inactivity and obesity.
The sum of obesity (7% of health care costs) and of inactivity (2.4%) is here used to estimate the total direct costs of inactivity. Overall a minimum 9.4% of all direct costs incurred in delivering health care in the U.S. are attributable to insufficient energy expenditure which directly leads to medical conditions or alternatively the accumulation of adiposity which then contributes to excess morbidity and mortality. As there are clear health benefits with increasing levels of physical activity, the definition of inactivity is somewhat arbitrary and could be raised so that more of the population is considered inactive. Under a broader definition of inactivity, more of the chronic conditions considered here would be attributable to lack of activity. Such changes would substantially increase the economic burden of lack of activity and of obesity or excess adiposity. As noted for obesity in The Netherlands, the majority of health care costs arise from the overweight rather than the obese population. This reflects the distribution of adiposity in the population, and the principle set forth by Rose, that disease arises not from the tails of the distribution but from those at average risk (41).
Note that these are conservative estimates of the current U.S. costs. The costs of obesity are estimated for those with BMI of 30 or more kilograms per meter squared. Adverse health affects are present at levels of obesity below a BMI of 30 (34,46) and higher levels of activity are associated with even lower risk of many chronic conditions (47). There are substantial additional costs incurred among those who are overweight (BMI 25 to 29.9; 32% of the U.S. population). Likewise for estimates of inactivity, we use the prevalence of approximately 28% of the U.S. population being inactive.
DISCUSSION
The public health burden of inactivity and obesity is substantial. Estimates of the proportion of deaths caused by these factors range from 14 to 23% of total mortality in the United States. The public health burden of inactivity is thus substantial for mortality but also for chronic conditions that negatively impact quality of life as well as life expectancy. Health consequences of sedentary lifestyle are independent of those associated with obesity as indicated in several major studies which have simultaneously evaluated physical activity and obesity in relation to colon cancer, diabetes, and total mortality. For example, evaluating relationships between physical activity and colon cancer, Giovannucci (13) and Martinez (27) found that the inverse associations with level of activity were independent of BMI. Likewise Blair has shown independent effects of fitness and activity on mortality (2,3). These and other data support the assumption of independence and hence allow us to add the economic costs of obesity to the costs of sedentary lifestyle. We therefore here added the direct costs of obesity to those for sedentary lifestyle.
The costs of inactivity and obesity are similar to the total estimated impact of cigarette smoking in the United States ($47 billion) (25). These costs of inactivity and obesity reflect, in large part, the impact of weight gain in adult life. These costs could be avoided if individuals maintained a healthy weight throughout adulthood. This is now a priority recommendation for the U.S. Department of Health and Human Service dietary and weight guidelines (46).
Gorsky et al. (15) simulated three hypothetical cohorts to estimate the costs of health care according to level of obesity over a 25-yr period, discounting future costs at 3% per year. They estimate that 16 billion additional dollars will be spent over the next 25 years treating health outcomes associated with obesity among middle-aged women. Using an incidence-based approach to cost of illness, Oster et al. (35) estimated the excess costs of health services according to level of obesity. Using a conservative approach that does not include any future weight gain and starting with NHANES3 population estimates for BMI, cholesterol, hypertension, and diabetes, they estimate the lifetime future costs per person as comparable with those of smoking.
A social cost that is not considered in any of the economic summaries is that of reduced physical functioning that is associated with higher levels of obesity (5,11). Inactivity or low levels of physical fitness are important determinants of loss of function, and weight training studies show improvements in function in frail elderly (9). Research is needed to quantify these relations and incorporate the deterioration in quality of life into summaries of the burden of inactivity.
While benign prostatic hyperplasia has not been considered here, it is noteworthy that this common condition may be but one of many complications of obesity and inactivity that has been overlooked. Likewise there is a direct relation between increasing adiposity and the diagnosis of infertility among young women (39). Recent evidence also suggests that obesity is related to asthma. This common condition which is rising in prevalence around the world is related to adiposity among children and also adults.
The recent interest in and documentation of relations between weight-bearing exercise and decreased risk of osteoporotic fractures of the hip points to important work remaining to be incorporated into economic costs of illness studies. Growing evidence that activity is associated with higher bone density and also with better muscle tone, together contributing to lower risk of falls and fractures (16,33,38,45), now points to the need for better estimates of the social and economic burden of hip fracture.
In summary, growing levels of both inactivity and obesity pose major health problems in Western society. These preventable sources of morbidity and mortality require focused strategies to increase the level of energy expenditure. Substantial benefits will likely accrue through reduced health care costs but also through reduction in the indirect costs as well as gains in quality of life.
Dr. Beverly Rockhill provided valuable input to the preparation of this manuscript.
This study was supported by Boston Obesity Nutrition Research Center, DK46200, and in part by CA40356.
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