ECONOMIC AND BUDGET ISSUE BRIEF

How Does Obesity in Adults Affect Spending on 

Health Care?

CBO A series of issue summaries from

the Congressional Budget Office

SEPTEMBER 8, 2010

Summary

Over the past two decades, the adult population in the 

United States has, on average, become much heavier. 

From 1987 to 2007, the fraction of adults who were 

overweight or obese increased from 44 percent to 

63 percent; almost two-thirds of the adult population 

now falls into one of those categories. The share of 

obese adults rose particularly rapidly, more than 

doubling from 13 percent to 28 percent. That sharp 

increase in the fraction of adults who are overweight or 

obese poses an important public health challenge. 

Those adults are more likely to develop serious 

illnesses, including coronary heart disease, diabetes, 

and hypertension. As a result, that trend also affects 

spending on health care.

This Congressional Budget Office (CBO) issue brief 

examines changes over time in the distribution of 

adults among four categories of body weight: underweight, normal, overweight, and obese. Those categories are defined in federal guidelines using a measure 

known as the body-mass index—a measure that 

standardizes weight for height. CBO analyzes how past 

changes in the weight distribution have affected health 

care spending per adult and projects how future 

changes might affect spending going forward. (In this 

issue brief, “health care spending” refers to spending 

by public and private insurers and out-of-pocket 

spending by individuals.)

According to CBO’s analysis of survey data, health 

care spending per adult grew substantially in all weight 

categories between 1987 and 2007, but the rate of 

growth was much more rapid among the obese 

(defined as those with a body-mass index greater than 

or equal to 30). Spending per capita for obese adults 

exceeded spending for adults of normal weight by 

about 8 percent in 1987 and by about 38 percent in 

2007. That increasing gap in spending between the 

two groups probably reflects a combination of factors, 

including changes in the average health status of the 

obese population and technological advances that offer 

new, costly treatments for conditions that are particularly common among obese individuals.

A relatively simple set of calculations using survey data 

indicates that if the distribution of adults by weight 

between 1987 and 2007 had changed only to reflect 

demographic changes, such as the aging of the population, then health care spending per adult in 2007 

would have been roughly 3 percent below the actual 

2007 amount. Similar calculations show the potential 

effects of different trends in adults’ body weight on 

future health care spending. CBO considered three 

scenarios. In all three, CBO assumed that per capita 

health care spending will continue to grow faster for 

adults whose weight is in the above-normal categories 

than for those whose weight is considered normal. 

CBO’s assumptions and findings for the scenarios are 

as follows: 

B First, CBO assumed that there will be no future 

changes in the distribution of adults by body weight 

and, therefore, that the prevalence of obesity will 

remain at the 2007 rate of 28 percent. If so, 

per capita spending on health care for adults would 

rise by 65 percent—from $4,550 in 2007 to $7,500 

in 2020, CBO estimates—largely as a result of the 

continuation of underlying trends in health care 

that have led to rapidly increasing spending for all 

adults regardless of weight. (All dollar figures are in 

2009 dollars.) 
2 CONGRESSIONAL BUDGET OFFICE

ECONOMIC AND BUDGET ISSUE BRIEF

Changes in Adults’ Body Weight 

Over the past several decades, the adult population in the 

United States has undergone a dramatic shift toward 

heavier body weight.1

 CBO’s analysis distinguishes four 

categories of weight standardized for height using the 

body-mass index (BMI), which equals an individual’s 

weight in pounds divided by height in inches squared 

and multiplied by 703.2 Those categories are defined in 

federal guidelines as follows: 

B Underweight—BMI less than 18.5; 

B Normal weight—BMI greater than or equal to 18.5 

and less than 25;

B Overweight—BMI greater than or equal to 25 and 

less than 30; and

B Obese—BMI greater than or equal to 30.

As used in this report, the last category includes people 

who are generally defined as obese but not morbidly 

obese (BMI greater than or equal to 30 and less than 40) 

and those who are morbidly obese (BMI greater than or 

equal to 40).3 Using the above criteria, a person who is 

five feet eight inches tall, for example, is considered 

Summary (Continued)

B Alternatively, CBO assumed a rising prevalence of 

obesity—namely, that recent trends (from 2001 to 

2007) in adults’ body weight will continue. In that 

scenario, the prevalence of obesity would rise to 

37 percent by 2020, and per capita spending would 

increase to $7,760—about 3 percent higher than 

spending in the first scenario.

B CBO also assessed the impact of a possible reversal 

in recent trends by assuming that, by 2027, the distribution of adults’ body weight will return to the 

1987 distribution (essentially reversing what happened from 1987 to 2007). In that scenario, the 

prevalence of obesity among adults would drop to 

20 percent by 2020. Per capita spending would 

increase to $7,230 in 2020—about 4 percent lower 

than spending in the first scenario.

Because lower rates of obesity are associated with better health and lower health care spending per capita, 

there is considerable interest in devising policies that 

would reduce the fraction of the population that is 

obese. Research and experimentation in this area are 

ongoing, but the literature to date suggests that the 

challenges involved in reducing the prevalence of 

obesity are significant. 

How reducing obesity would affect both total (rather 

than per capita) spending for health care and the federal budget over time is less clear. To the extent that 

people, on average, lived longer because fewer individuals were obese, savings from lower per capita spending 

would be at least partially offset by additional expenditures for health care during those added years of life. 

Moreover, the impact on the federal budget would 

include not only changes in federal spending on health 

care but also changes in tax revenues and in spending 

for retirement programs such as Social Security, for 

which costs are directly tied to longevity. As a result, 

the net impact of reductions in obesity rates on 

national health care expenditures and on federal budget deficits would depend on the magnitude of those 

various effects. This brief does not address the changes 

in longevity that might arise from a changing weight 

distribution or the potential impact of such changes on 

total health care expenditures.

1. The recent rise in excess weight among children is not addressed 

in this report but also raises important concerns. Data from the 

Centers for Disease Control and Prevention show that about 

17 percent of children ages 6 to 19 are currently overweight or 

obese, roughly triple the rate observed 30 years ago. Obesity 

appears to persist from childhood to adulthood, so higher rates of 

overweight or obesity among children are likely to yield higher 

rates of obesity among adults in the future than would occur if 

childhood obesity rates were lower.

2. The metric calculation of BMI equals weight in kilograms divided 

by height in meters squared. 

3. See National Institutes of Health, Clinical Guidelines on the 

Identification, Evaluation, and Treatment of Overweight and Obesity 

in Adults: The Evidence Report, NIH Publication No. 98-4083 

(September 1998), p. xiv, www.nhlbi.nih.gov/guidelines/obesity/

ob_gdlns.pdf. As defined by NIH, the “obese but not morbidly 

obese” category includes both Class I and Class II obesity, and the 

“morbidly obese” category corresponds to Class III obesity.
ECONOMIC AND BUDGET ISSUE BRIEF

HOW DOES OBESITY IN ADULTS AFFECT SPENDING ON HEALTH CARE? 3

Table 1.

Distribution of Adults and Health Care Spending per Adult, by Body Weight, 

1987 and 2007

Source: Congressional Budget Office based on the 1987 National Medical Expenditure Survey and the 2007 Medical Expenditure 

Panel Survey.

Notes: Weight categories are defined using the body-mass index (BMI)—a measure of weight standardized for height that applies to

adult men and women—as follows: underweight (BMI is less than 18.5); normal (greater than or equal to 18.5 and less than 25); 

overweight (greater than or equal to 25 and less than 30); obese but not morbidly obese (greater than or equal to 30 and less 

than 40); and morbidly obese (greater than or equal to 40).

The term “obese,” as used in this brief, combines the two categories of “obese but not morbidly obese” and “morbidly obese.” 

n.a. = not applicable.

a. The estimates for the population share and spending per adult in the underweight and morbidly obese categories are based on small 

samples and should therefore be interpreted with caution.

underweight if he or she weighs less than 122 pounds; 

normal weight (between 122 and 164 pounds); overweight (between 164 and 197 pounds); obese but not 

morbidly obese (between 197 and 263 pounds); or 

morbidly obese (over 263 pounds).

BMI is not a direct measure of body fat in that it does not 

distinguish fat from muscle and does not identify how 

body fat is distributed (around the abdomen or overall)—

characteristics that affect people’s health. Nonetheless, it 

is highly correlated with the risk of disease and death. It is 

also widely used by health care providers, because it is 

easy to collect, and by researchers, because it is available 

in household surveys.4

Although obesity rates began to rise around 1980 or earlier, the analysis in this issue brief focuses on the period 

from 1987 to 2007 because detailed survey data are available on spending for health care over that period. CBO 

analyzed data on the noninstitutionalized population 

age 19 or older from the 1987 National Medical Expenditure Survey (NMES) and the 2001 and 2007 Medical 

Expenditure Panel Surveys (MEPS). Those surveys 

include information on individuals’ demographic characteristics, medical conditions, use of health care services, 

and health care expenditures.5

 Estimates of BMI are 

based on self-reported height and weight, which have 

been shown to be lower than estimates based on actual 

measurements. CBO’s findings would not be affected by 

such misreporting, however, if the relationship between 

self-reported and measured height and weight has 

remained roughly constant over time. 

4 2 3,230 4,970 -50 54

52 35 2,440 4,030 -33 65

31 35 2,650 4,260 13 61

Obese 13 28 2,630 5,560 115 111

12 24 2,640 5,330 100 102

1 4 2,530 7,010 300 177

All Categories 100 100 2,560 4,550 n.a. 78

 Obese but not morbidly obese

Spending per Adult 1987–2007

Percentage Change, 

1987 2007 1987 2007

Share of Adult

(2009 dollars)

Population

Population (Percent) Share of Adult Spending 

Weight Category

Underweighta

Normal

Overweight

per Adult

 Morbidly obesea

4. For a discussion of different measures of obesity, see Richard V. 

Burkhauser and John Cawley, “Beyond BMI: The Value of More 

Accurate Measures of Fatness and Obesity in Social Science 

Research,” Journal of Health Economics, vol. 27, no. 2 (March 

2008), pp. 519–529.

5. Health care spending is reported as charges in the 1987 NMES 

but as payments in the 2007 MEPS. To make the data 

comparable, CBO converted charges to payments using the 

methods suggested in Samuel H. Zuvekas and Joel W. Cohen, 

“A Guide to Comparing Health Care Expenditures in the 1996 

MEPS to the 1987 NMES,” Inquiry, vol. 39, no. 1 (Spring 2002), 

pp. 76–86. 
4 CONGRESSIONAL BUDGET OFFICE

ECONOMIC AND BUDGET ISSUE BRIEF

The fraction of adults who were obese rose from 13 percent in 1987 to 28 percent in 2007 (see Table 1). The 

share of adults who were overweight increased slightly 

during that period, and the share whose weight was 

within the range that health professionals consider “normal” declined from 52 percent to 35 percent.6 Another 

survey indicated similar changes in obesity rates during 

that period but measured an even higher share of the 

population—more than one-third—as obese in the 

2003–2006 period.7

The rate of growth in the share of adults who were obese 

may have slowed in recent years, but different data 

sources provide varying indications of the extent of that 

slowing. In the survey data that CBO analyzed, the share 

of adults who were obese rose from about 13 percent to 

24 percent between 1987 and 2001—the first year in 

which a consistent BMI measure for adults was available 

in the MEPS—or about 0.8 percentage points per year, 

on average; from 2001 to 2007, that share rose to 

28 percent, for an average increase of 0.7 percentage 

points per year, nearly as rapid an increase as in the earlier 

period.8

 In contrast, data from the National Health and 

Nutrition Examination Survey (NHANES), in which 

BMI is calculated using measured rather than selfreported height and weight, suggest that the growth in 

the prevalence of obesity may be slowing much more, 

especially for women. According to those data, that 

growth averaged 0.84 percentage points a year for men 

and 0.95 percentage points for women between the 

periods 1988–1994 and 1999–2000 but dropped to only 

0.59 percentage points per year for men and 0.26 percentage points for women between the periods 1999–

2000 and 2007–2008.9 Both sets of data, however, 

indicate that the prevalence of obesity is continuing to 

rise. Even at the smaller growth rates indicated by the 

NHANES, the fraction of adults who are obese would 

grow by between 4 and 5 percentage points in 10 years.

Demographic changes can explain part of the overall rise 

in the prevalence of obesity. For example, an adult is 

more likely to be obese between the ages of 40 and 60 

than at other ages, and the fraction of adults within that 

age range rose from 30 percent in 1987 to 39 percent in 

2007. Even so, the data CBO analyzed indicate that 

demographic changes—including changes in the distribution of adults by age, sex, and race—can explain only 

8 percent of the rise in the fraction of obese adults over 

that period. Although more research is warranted, one 

study found that the rise in obesity rates in the United 

States is related mostly to an increase in caloric intake—

and, in particular, an increase in calories from snacks—

rather than to a decline in physical activity.10

Changes in Health Care Spending by 

Weight Category 

Being overweight or obese raises an adult’s risk of developing a number of serious illnesses, and the risk is greater 

for obese individuals.11 Those illnesses include coronary 

heart disease, diabetes, and hypertension. Excess weight 

might also increase the severity of certain diseases not 

6. Only a relatively small fraction of adults are underweight, and that 

share fell by roughly half from 1987 to 2007. Some patients who 

have severe health problems may experience unhealthy weight loss 

as a result of their illness or as a side effect of treatment. Thus, 

unlike the other changes in the weight distribution, which generally suggest unhealthy weight gains, the fall in the fraction of 

underweight adults might at least partly reflect an improvement in 

health. 

7. According to data gathered by the National Center for Health 

Statistics (NCHS), the share of adults who were obese increased 

from 23 percent in the 1988–1994 period to 34 percent in the 

2003–2006 period. See NCHS, Health, United States, 2009

(January 2010), p. 302. That survey includes measures of height 

and weight that are more accurate than the self-reported measures 

available in the data that CBO analyzed, but the NCHS survey 

does not collect information about spending on health care and is 

therefore less useful for this analysis. 

8. A recent study showed similar growth in the prevalence of obesity 

“Vital Signs: State-Specific Obesity Prevalence Among Adults—

United States, 2009,” Morbidity and Mortality Weekly Report,

vol. 59 (August 3, 2010). That study calculates BMI using selfreported height and weight from the Behavioral Risk Factor 

Surveillance System. 

9. Katherine M. Flegal and others, “Prevalence and Trends in Obesity Among US Adults, 1999–2008,” Journal of the American Medical Association, vol. 303, no. 3 (January 20, 2010), pp. 235–241.

10. David M. Cutler, Edward L. Glaeser, and Jesse M. Shapiro, “Why 

Have Americans Become More Obese?” Journal of Economic 

Perspectives, vol. 17, no. 3 (Summer 2003), pp. 93–118.

11. Obesity also appears to reduce longevity. A number of studies 

have found, however, that being overweight but not obese does 

not affect longevity for adults. (See, for example, Katherine M. 

Flegal and others, “Excess Deaths Associated with Underweight, 

Overweight, and Obesity,” Journal of the American Medical Association, vol. 293, no. 15 (April 20, 2005), pp. 1861–1867.) This 

issue brief does not address the relationship between excess weight 

and longevity.
ECONOMIC AND BUDGET ISSUE BRIEF

HOW DOES OBESITY IN ADULTS AFFECT SPENDING ON HEALTH CARE? 5

directly caused by it. Not surprisingly, then, health care 

spending for adults whose weight is above normal is 

higher than for those whose weight is normal. That 

difference, which was small several decades ago, has 

remained relatively stable for overweight adults but has 

widened substantially for obese adults.12

Health Care Spending per Adult

Health care spending per adult (in 2009 dollars) rose 

close to 80 percent from 1987 to 2007, from about 

$2,560 to $4,550, driven in part by the development and 

diffusion of new medical technology, more extensive 

insurance coverage, the aging of the population, and rising real (inflation-adjusted) prices for health care services. 

That spending grew substantially among all weight categories, but in the data that CBO analyzed, the rate of 

growth was much more rapid among the obese (see 

Figure 1). For example, from 1987 to 2007, per capita 

spending grew by 65 percent for normal-weight adults 

and by 61 percent for overweight adults, but grew much 

faster for obese adults—by 111 percent (see Table 1 on 

page 3). As a result, per capita spending for obese adults 

was far higher relative to spending for normal-weight 

adults in 2007 than it was in 1987; that difference rose 

from 8 percent in 1987 to 38 percent 20 years later. 

Spending per Adult on Obesity-Related Diseases

To what extent are the differences in average spending 

between normal-weight and obese adults attributable to 

obesity, and to what extent are they attributable to other 

factors that are correlated with, rather than a direct result 

of, obesity? (For example, obese adults may have other 

personal characteristics or habits that result in higher 

spending on health care.) To the extent that they are 

merely correlated, attributing the differences in spending 

to obesity would overstate the effect of obesity on health 

care spending. 

To examine that question, CBO identified the amount of 

total health care spending devoted to treating diseases 

that medical researchers have linked to obesity.13 If the 

gap in per capita spending from one weight category to 

the next can be explained by the cost of treating those 

diseases, the difference in total health care spending for 

adults in the various weight categories is probably attributable to obesity. Alternatively, if per capita spending on 

obesity-related diseases explains little of the gap, factors 

other than body weight may account for those differences.14 A similar test examines how much of the variation over time in the total spending gap from one weight 

category to the next can be explained by changes over 

time in the differences in spending on obesity-related 

diseases between those categories.

As one might expect, spending on the obesity-related 

conditions CBO identified is generally higher for heavier 

adults, but normal-weight adults also develop those conditions—reflecting the fact that obesity is only one of the 

risk factors associated with those conditions. For example, spending in 2007 on obesity-related diseases averaged 

$2,030 for obese adults and $1,090 for normal-weight 

adults, a difference of $940 (see Table 2). Therefore, 

spending on the obesity-related diseases CBO considered 

accounts for about 60 percent of the $1,530 difference in 

total spending on health care per capita between normalweight and obese adults in that year. That finding leaves 

about 40 percent of the spending differential unexplained 

12. Other studies have looked at how changes in obesity rates affect 

health care spending. See, for example, The Future Costs of Obesity: 

National and State Estimates of the Impact of Obesity on Direct 

Health Care Expenses (a collaborative report from the United 

Health Foundation, the American Public Health Association, 

and the Partnership for Prevention, updated November 2009), 

www.fightchronicdisease.org/pdfs/CostofObesityReportFINAL.pdf; Eric A. Finkelstein and others, “Annual Medical 

Spending Attributable to Obesity: Payer- and Service-Specific 

Estimates,” Health Affairs, Web Exclusive (July 27, 2009), 

pp. w822–w831; Darius N. Lakdawalla and others, “The 

Health and Cost Consequences of Obesity Among the Future 

Elderly,” Health Affairs, Web Exclusive (September 26, 2005); 

and Kenneth E. Thorpe and others, “The Impact of Obesity on 

Rising Medical Spending,” Health Affairs, Web Exclusive 

(October 20, 2004), pp. w4-480 to w4-486.

13. The obesity-related diseases examined in this analysis include coronary heart disease, type II diabetes, certain cancers, hypertension, 

dyslipidemia (for example, high total cholesterol), stroke, liver and 

gallbladder disease, osteoarthritis, certain gynecological problems, 

and some depressive disorders.

14. This approach is not a perfect one because there is not a clear 

divide between obesity-related diseases and other diseases. Instead, 

errors are possible in both directions. CBO’s analysis could understate the true impact of obesity because diseases other than the 

ones considered may also be connected to obesity in a less direct 

way and, hence, additional spending might be caused by excessive 

body weight. Working in the other direction, the survey data do 

not distinguish principal from secondary diagnoses and thus may 

encompass spending for care that is only tangentially connected 

to an obesity-related disease. Although those errors are hard to 

quantify, the first one is probably larger than the second.
6 CONGRESSIONAL BUDGET OFFICE

ECONOMIC AND BUDGET ISSUE BRIEF

Figure 1.

Distribution of Adults and Health Care Spending per Adult, by Body Weight, 

1987 and 2007

(2009 dollars)

Source: Congressional Budget Office based on the 1987 National Medical Expenditure Survey and the 2007 Medical Expenditure 

Panel Survey.

Note: The width of each bar represents the relative share of the population in each category. Weight categories are defined using the bodymass index (BMI)—a measure of weight standardized for height that applies to adult men and women—as follows: underweight (BMI 

is less than 18.5); normal (greater than or equal to 18.5 and less than 25); overweight (greater than or equal to 25 and less than 30); 

obese but not morbidly obese (greater than or equal to 30 and less than 40); and morbidly obese (greater than or equal to 40).

a. The estimates for the population share and spending per adult in the underweight category are based on small samples and should 

therefore be interpreted with caution.

b. The term “obese,” as used in this brief, combines the two categories of “obese but not morbidly obese” and “morbidly obese.”

and perhaps attributable to factors other than body 

weight.

As for the growth in the gap in total health care spending 

per capita between normal-weight and obese adults from 

1987 to 2007, about half appears to be attributable to 

obesity-related diseases. In particular, that gap grew from 

$190 in 1987 to $1,530 in 2008, an increase of $1,340. 

Over that same period, the gap in spending on obesityrelated diseases between normal-weight and obese adults 

grew by $670, accounting for about 50 percent ($670 

divided by $1,340) of that increase. Thus, a little more 

than half of the difference in total health care spending 

between normal-weight and obese adults in 2007 and 

half of the growth in that difference since 1987 appears to 

be attributable to obesity-related diseases. 

1987 2007

0

1,000

2,000

3,000

4,000

5,000

6,000

Underweighta

Normal

Overweight

Obeseb
ECONOMIC AND BUDGET ISSUE BRIEF

HOW DOES OBESITY IN ADULTS AFFECT SPENDING ON HEALTH CARE? 7

Table 2.

Changes in Total and Obesity-Related Spending on Health Care for Adults, 

by Body Weight, 1987 to 2007

Source: Congressional Budget Office based on the 1987 National Medical Expenditure Survey and the 2007 Medical Expenditure 

Panel Survey. 

Notes: Weight categories are defined using the body-mass index (BMI)—a measure of weight standardized for height that applies to adult 

men and women—as follows: underweight (BMI is less than 18.5); normal (greater than or equal to 18.5 and less than 25); overweight (greater than or equal to 25 and less than 30); obese but not morbidly obese (greater than or equal to 30 and less than 40); 

and morbidly obese (greater than or equal to 40).

The term “obese,” as used in this brief, combines the two categories of “obese but not morbidly obese” and “morbidly obese.”

The obesity-related diseases examined in this analysis include coronary heart disease, type II diabetes, certain cancers, hypertension, 

dyslipidemia (for example, high total cholesterol), stroke, liver and gallbladder disease, osteoarthritis, certain gynecological problems, 

and some depressive disorders.

n.a. = not applicable.

a. The estimates for spending per adult in the underweight and morbidly obese categories are based on small samples and should therefore 

be interpreted with caution.

Those estimates suggest that a large part of the difference 

in total health care spending per capita between normalweight and obese adults is a direct result of differences in 

body weight. When estimating changes in overall per 

capita spending as a result of changes in the prevalence of 

obesity, CBO assumed that excess weight accounts for 

three-quarters of the difference in spending between 

normal-weight and obese adults, reflecting the analysis 

above with an upward adjustment for the probable 

omission of obesity-related conditions and conditions 

that are made worse by excess weight.15 Therefore, when 

an adult who would have appeared in the obese weight 

category instead appears in the normal weight category, 

spending for that individual equals three-quarters of the 

spending for normal-weight adults plus one-quarter of 

the spending for obese adults. Conversely, when an adult 

who would have appeared in the normal weight category 

instead appears in the obese category, spending for that 

Weight Category 1987 2007 1987 2007

Underweighta 3,230 4,970 1,740 260 1,740 1,480 8 35 85

Normal 2,440 4,030 1,590 390 1,090 700 16 27 44

Overweight 2,650 4,260 1,610 540 1,390 850 20 33 53

Obese 2,630 5,560 2,930 660 2,030 1,370 25 37 47

Obese but not morbidly obese 2,640 5,330 2,690 640 1,910 1,270 24 36 47

Morbidly obesea 2,530 7,010 4,480 780 2,770 1,990 31 40 44

All Categories 2,560 4,550 1,990 470 1,470 1,000 18 32 50

Memorandum:

Excess Spending for Obese 

Relative to Normal

In 2009 dollars 190 1,530 1,340 270 940 670 142 61 50

In percent 8 38 84 69 86 96 n.a. n.a. n.a.

Diseases as a 

Obesity-Related

Diseases per Adult

1987–2007

Change, 

(2009 dollars)

Spending on Obesity-Related 

Total Spending per Adult 

1987–2007

Spending on 

1987 2007

Total Spending 

Percentage of 

1987–2007

Obesity-Related

(2009 dollars) Changes in

Change, 

Spending as a

Percentage of 

Total Spending,

15. CBO tested the sensitivity of the estimates in this brief to that 

assumption by computing spending under two alternative 

assumptions: that excess weight accounts for half or all of the 

difference in spending between normal-weight and obese adults. 

Those results were quite similar to the ones presented in this brief.
8 CONGRESSIONAL BUDGET OFFICE

ECONOMIC AND BUDGET ISSUE BRIEF

individual equals one-quarter of the spending for normalweight adults plus three-quarters of the spending for 

obese adults.16

For adults in the normal weight category who would 

otherwise have been overweight, CBO assumed that 

spending for their health care would equal that for 

normal-weight adults. The reason is that excess body 

weight appears to explain all of the difference in total 

spending between those two weight categories. In 2007, 

for instance, the gap in spending between normal-weight 

and overweight adults ($4,260 minus $4,030, or $230), 

shown in Table 2, can be more than fully explained by 

differences in obesity-related spending ($1,390 minus 

$1,090, or $300).17

Factors Contributing to the Growing 

Differences in Health Care Spending 

Between Normal-Weight and Obese Adults

Several factors may account for the growing gap in health 

care spending between normal-weight and obese adults. 

They include changes in the relative health of obese 

people and changes in treatments for obesity-related 

diseases.18

Changes in Health Status. The relatively rapid growth in 

spending for obese adults may reflect changes in the 

health status of the obese population from 1987 to 2007. 

Adults who are currently obese might be in poorer health 

than those who were obese in 1987, because advances in 

medical treatment in recent decades may have reduced 

the mortality rates for some obesity-related conditions. 

As a result, some obese individuals with severe health 

problems who would have died relatively young in past 

decades are probably living longer and accounting for 

continued spending on health care that is high even 

relative to spending on care for other obese adults.

Another potential reason for the rapid growth in spending for obese adults is that adults who were obese in 2007 

may have had excess weight for longer periods of time 

than their 1987 counterparts, as suggested by the upward 

trends in the likelihood that children will be overweight 

or obese. The adverse effects of obesity on an individual’s 

health seem likely to accumulate over time, so obesityrelated health care spending for adults who have been 

obese for a prolonged period is probably higher, in 

general, than for those who recently became obese. 

Changes in Medical Technology and Providers’ Practice 

Patterns. Technological change in medicine has increased 

health care spending per adult for all weight categories by 

expanding the set of available medical services, and those 

technological changes may have had a relatively large 

impact on health care spending for obese adults.19 The 

rise in obesity’s prevalence also may have promoted more 

aggressive use of existing technology for obese people or 

hastened the development of technologies that were 

aimed at treating obesity-related conditions. 

Effects of Past Changes in Body Weight on 

Health Care Spending

Determining what would have happened to health care 

spending if obesity rates had not increased is difficult, 

because it is hard to know what other aspects of the 

health care system might also have turned out differently—including the types of treatments developed and 

provided, the extent of insurance coverage purchased, and 

the federal payments made for health care. 

A rough answer can be provided by estimating what 

would have happened to per capita spending if the distribution of adults by body weight had changed only to 

reflect demographic changes (that is, if individuals in 

each age, sex, and race group did not become heavier 

during that period) but per capita spending in a given 

weight category changed as observed. Under those 

circumstances, CBO estimates, health care spending per 

adult in 2007 would have been $4,400, about 3 percent 

less than the amount actually observed in the data 

($4,550). That estimate is based on a calculation in 

which spending for the 15 percent of adults who were 

overweight or obese in 2007 (but who would have been 

16. This assumption applies to both categories of obese adults—

“obese but not morbidly obese” and “morbidly obese.” 

17. Analogously, when adults who would otherwise have been in the 

normal weight category instead appear in the overweight category, 

they are assigned the spending of an overweight adult.

18. Some of the measured differences in spending also may occur 

because of the way in which the data were collected. The 1987 

and the 2007 data come from different surveys, and the way 

the two surveys measured health care spending was not fully 

consistent.

19. For examples of recently developed therapies and a discussion of 

technological change and health care spending, see Congressional 

Budget Office, Technological Change and the Growth of Health 

Care Spending (January 2008). 
ECONOMIC AND BUDGET ISSUE BRIEF

HOW DOES OBESITY IN ADULTS AFFECT SPENDING ON HEALTH CARE? 9

of normal weight if the weight distribution within 

demographic groups had not changed since 1987) would 

have been roughly 20 percent lower than if they were 

overweight or obese (on the basis of CBO’s assumptions 

about the share of spending differences attributable to 

excess weight). 

Potential Effects of Future Changes in 

Body Weight on Health Care Spending

Two decades ago, health care spending was somewhat 

higher for obese adults than for normal-weight adults, 

but the differences were relatively small; a change in the 

fraction of adults who were obese—even a large change—

would therefore have had little effect on overall spending 

at that time. Currently, however, differences in the weight 

distribution exert much more influence on spending 

because of the much wider gap in per capita spending 

between normal-weight and obese adults. Therefore, a 

rise in the prevalence of obesity of a given magnitude in 

future years would have a greater impact on average 

spending per adult than a rise of comparable magnitude 

would have had at an earlier time, particularly if the 

trends in per capita spending observed in the survey data 

between 1987 and 2007 among the respective weight 

categories continued. 

Projected Spending in 2020 Under Various 

Assumptions About Body Weight

To illustrate the potential impact of changes in body 

weight on future health care spending, CBO projected 

spending in 2020 using different assumptions about 

future trends in the distribution of adults and of health 

care spending per adult by weight category.20 Specifically, 

CBO modeled three scenarios, all of which incorporate 

changes in the demographic (age, sex, and race) 

composition of the adult population as projected by the 

U.S. Census Bureau. In addition, CBO assumed that 

per capita health care spending will continue to grow 

faster for adults whose weight is in the above-normal 

categories than for those whose weight is considered 

normal.21

Scenario 1: Distribution by Body Weight Remains 

Unchanged from 2007. Under this scenario, individuals 

within each demographic category—grouped by age, sex, 

and race—do not become heavier over time, but body 

weight continues to rise slightly because of aging and 

other shifts among demographic categories. Under those 

assumptions, the share of obese adults would remain at 

about 28 percent in 2020, and spending per adult would 

rise from $4,550 in 2007 to $7,500 in 2020 (see 

Table 3)—largely as a result of the underlying trends in 

health care that are projected to increase spending for all 

adults regardless of weight (all dollar figures are in 2009 

dollars).22

Scenario 2: Distribution by Body Weight Changes at the 

Average Annual Rates for the 2001–2007 Period. This 

scenario assumes that recent trends in adults’ body weight 

continue. By 2020, the share of obese adults would reach 

37 percent. Projected spending per capita would be 

$7,760—about 3 percent higher than in the first 

scenario. 

Scenario 3: Distribution by Body Weight Returns to the 

1987 Distribution by 2027. This scenario represents a 

reversal of the sharp rise in the percentage of the adult 

population with above-normal weight that has occurred 

since 1987. That steep decline would result in 20 percent 

of adults being obese in 2020. Projected spending per 

capita would be $7,230—that is, 4 percent lower than in 

Scenario 1 and about 7 percent lower than in Scenario 2. 

Even though obesity rates in this scenario would be lower 

in 2020 than in 2007, health care spending per capita 

would be higher, reflecting a continuing increase in 

underlying health care spending and in the gap in 

spending between normal-weight and obese adults.

Discussion of the Results

The estimates in all three scenarios are subject to considerable uncertainty, for several reasons. One reason is that 

the rate of growth in spending for obese adults relative to 

that for normal-weight adults is uncertain. If it were 

20. This issue brief uses the projections of health care spending 

described in Congressional Budget Office, The Long-Term Budget 

Outlook (June 2010, revised August 2010).

21. In 2007, spending was 38 percent higher for obese adults than for 

normal-weight adults. Under the assumptions used in CBO’s 

analysis, spending in 2020 is projected to be 69 percent higher for 

obese adults. 

22. Rounding makes the share of obesity appear unchanged. In fact, 

that share rises by 0.25 percentage points from 2007 to 2020.
10 CONGRESSIONAL BUDGET OFFICE

ECONOMIC AND BUDGET ISSUE BRIEF

Table 3.

Projected Prevalence of Obesity and Health Care Spending per Adult in 2020 

Under Alternative Scenarios

Source: Congressional Budget Office based on the 1987 National Medical Expenditure Survey and the 2001 and 2007 Medical Expenditure 

Panel Surveys.

Notes: Spending for 2007—the most recent year available—is based on estimates from that year’s Medical Expenditure Panel Survey.

CBO projected spending for 2020 under three scenarios, which are described in the text.

n.a. = not applicable.

a. The term “obese,” as used in this brief, combines the two categories of “obese but not morbidly obese” and “morbidly obese.”

lower than assumed, then the projected impacts of 

changes in the weight distribution on spending per adult 

over the next 10 years would be smaller than those that 

CBO estimated; if it were higher than assumed, those 

impacts would be larger.

In addition, a change in the prevalence of obesity could 

be reached by many paths, and those paths could have 

different implications for spending. For example, obesity 

rates could be lower if younger adults never became 

obese, which would reduce health care spending for that 

cohort. Alternatively, lower obesity rates could be 

achieved if adults who were already obese lost weight; but 

the harmful effect of obesity on health might not be fully 

reversible, particularly for those who have been obese for 

a prolonged period. As a result, the impact on spending 

might well be different in that case. 

In all three scenarios, how changes in the distribution of 

adults by body weight would affect total (rather than per 

capita) spending for health care over multiple years is 

ambiguous. To the extent that the distribution changed 

because fewer people were obese, and therefore people 

lived longer on average, savings from lower per capita 

spending would be offset somewhat by additional expenditures incurred during those added years of life. (The 

opposite would be true if there were a trend toward a 

higher prevalence of obesity.) The net impact of changes 

in the weight distribution on total health care spending 

would therefore depend on the magnitude of those 

opposing effects. Moreover, the impact on the federal 

budget would include not only the effects on federal 

spending for health care but also the effects on tax 

revenues and on spending for Social Security and other 

programs that are tied to longevity. 

Implications for Policy Initiatives

The illustrative calculations above indicate that a 

reduction in adults’ body weight would result in lower 

per capita spending on health care. However, designing 

public policies to reduce health care spending by preventing future cases of obesity or achieving significant and 

sustained weight loss among overweight and obese adults 

Percentage of Adults

Who Are Obesea 28 28 37 20

Spending per Adult

In 2009 dollars 4,550 7,500 7,760 7,230

Percentage difference

relative to Scenario 1 n.a. n.a. 3 -4

Percentage change,

2007–2020 n.a. 65 71 59

Actual 

2007

Scenario 1: 

Distribution by 

Body Weight Remains 

Unchanged from 2007

Scenario 2: 

Distribution by Body Weight

Scenario 3: 

Changes at the Average Annual

Rates for the 2001–2007 Period Distribution by 2027

Weight Returns to the 1987

Distribution by Body 
ECONOMIC AND BUDGET ISSUE BRIEF

HOW DOES OBESITY IN ADULTS AFFECT SPENDING ON HEALTH CARE? 11

is difficult.23 In many cases, obesity is the result of poor 

diet and lack of exercise, both of which can be hard to 

change. Indeed, the evidence on the impact of various 

approaches to weight loss suggests that most adults who 

lose weight have a difficult time maintaining the weight 

loss without continued intervention, such as a program 

for improving nutrition or increasing exercise.24 The 

costs of ongoing interventions are likely to offset at least 

part of any reductions in health care spending attributable to weight loss, although the improvements in health 

that would result might still make the interventions an 

appropriate use of public or private funds. 

Another issue concerns the relatively large increases 

during the past few decades in per capita spending for 

obese adults compared with spending for normal-weight 

adults. Policy initiatives aimed at reducing the prevalence 

of obesity would not directly affect the gap in per capita 

spending between the two groups, especially if that 

increasing gap was caused by changes in the treatment of 

obesity-related conditions. (Indeed, the three scenarios 

assume that the gap in per capita spending between the 

two groups continues to widen.) Therefore, another 

approach to reducing the spending associated with 

obesity would be to identify the factors responsible for 

that growing gap and ways to limit their influence on 

spending. 23. See Anjali Jain, What Works for Obesity? A Summary of the Research 

Behind Obesity Interventions (paper prepared for the United 

Health Foundation, London, U.K., and published by BMJ Publishing Group, April 2004), www.unitedhealthfoundation.org/

obesity.pdf; and Institute of Medicine, Health and Behavior: The 

Interplay of Biological, Behavioral, and Societal Influences

(Washington, D.C.: National Academies Press, 2001). For 

additional discussion and sources, see Congressional Budget 

Office, Key Issues in Analyzing Major Health Insurance Proposals

(December 2008), pp. 132–136. 

24. See National Institutes of Health, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in 

Adults, p. 69.

This brief was prepared by Noelia Duchovny and 

Colin Baker (formerly of CBO). It and other CBO 

publications are available at the agency’s Web site 

(www.cbo.gov).

Douglas W. Elmendorf 

Director