Will All Americans Become Overweight or Obese? Estimating the Progression and Cost of the US Obesity Epidemic

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1 nture publishing group rticles Will All s Become Overweight or Obese? Estimting the Progression nd Cost of the US Obesity Epidemic Youf Wng 1, My A. Beydoun 1, Ln Ling 2, Benjmin Cbllero 1 nd Shiriki K. Kumnyik 3 We projected future prevlence nd BMI distribution bsed on ntionl survey dt (Ntionl Helth nd Nutrition Exmintion Study) collected between 197s nd 24. Future obesity-relted helth-cre costs for dults were estimted using projected prevlence, Census popultion projections, nd published ntionl estimtes of per cpit excess helth-cre costs of obesity/overweight. The objective ws to illustrte potentil burden of obesity prevlence nd helth-cre costs of obesity nd overweight in the United Sttes tht would occur if current trends continue. Overweight nd obesity prevlence hve incresed stedily mong ll US popultion groups, but with notble differences between groups in nnul increse rtes. The increse (percentge points) in obesity nd overweight in dults ws fster thn in children (.77 vs ), nd in women thn in men (.91 vs..65). If these trends continue, by 23, 86.3% dults will be overweight or obese; nd 51.1%, obese. Blck women (96.9%) nd - men (91.1%) would be the most ffected. By 248, ll dults would become overweight or obese, while women will rech tht stte by 234. In children, the prevlence of overweight (BMI 95th percentile, 3%) will nerly double by 23. Totl helth-cre costs ttributble to obesity/overweight would double every decde to billion US dollrs by 23, ccounting for 16 18% of totl US helth-cre costs. We continue to move wy from the Helthy People 21 objectives. Timely, drmtic, nd effective development nd implementtion of corrective progrms/policies re needed to void the otherwise inevitble helth nd societl consequences implied by our projections. Obesity (28) 16, doi:1.138/oby Introduction Obesity hs become public helth crisis in the United Sttes. Ntionlly representtive survey dt show tht the prevlence hs stedily incresed over the pst three decdes lthough there re lrge disprities between popultion groups nd continuing chnges in the ssocited ptterns (1 3). Current evidence suggests tht the prevlence is likely to remin on the rise (1,4,5), nd it will not be possible to meet the objectives set for Helthy People 21 of reducing obesity prevlence in dults to 15% nd in children to 5% (6). Obesity hs mny helth, socil, psychologicl, nd economic consequences for the individuls being ffected nd for the society (7). The current US genertion my hve shorter life expectncy thn their prents if this obesity epidemic cnnot be controlled (8). The economic impct is especilly evident in helth-cre costs (9 13). A recent study estimted tht medicl expenditures ttributed to overweight nd obesity ccounted for 9.1% of totl US medicl expenditures in 1998 nd might hve reched 78.5 billion US dollrs (1). Expenditures will continue to rise prticulrly due to the increses in obesity prevlence nd in the cost of relted helth cre (11). This study ims to provide thorough nlysis to illustrte potentil future trends in obesity nd the relted helth-cre costs were current trends to continue, bsed on ntionlly representtive survey dt collected over the pst three decdes, to chrcterize the need for ntionl polices nd progrms. Such informtion will help the United Sttes nd perhps other policy mkers, helth professionls, nd the generl public to be better prepred to fce the relted chllenges, nd motivte the development of public helth nd clinicl progrms to ddress the obesity epidemic in order to void the mny dverse helth nd socil consequences tht will otherwise ensue. METHODS nd procedures Overview Our projection nlyses were bsed on prevlence dt from the Ntionl Helth nd Nutrition Exmintion Study (NHANES) 1 Center for Humn Nutrition, Deprtment of Interntionl Helth, Johns Hopkins Bloomberg School of Public Helth, Bltimore, Mrylnd, USA; 2 Center for Finncing, Access nd Cost Trends, Agency for Helthcre Reserch nd Qulity, Rockville, Mrylnd, USA; 3 Deprtment of Biosttistics nd Epidemiology, University of Pennsylvni School of Medicine, Phildelphi, Pennsylvni, USA. Correspondence: Youf Wng (ywng@jhsph.edu) Received 8 Jnury 28; ccepted 15 Mrch 28; published online 24 July 28. doi:1.138/oby obesity VOLUME 16 NUMBER 1 OCTOBER

2 collected between the 197s nd 24 (ref. 14). Compred with other vilble dt sources, the NHANES provides high qulity, directly mesured height nd weight dt from ntionlly representtive smples, nd the dt re comprble over time (1). Our projections of obesity-relted helth-cre costs re minly bsed on recently published studies using ntionl helth-cre expenditure dt. Key outcome vribles Overweight nd obesity. For prcticl purposes nd mong both children nd dults, BMI (weight (kg)/height (m) 2 ) is widely used nowdys to ssess obesity (15 18). In dults, the BMI (kg/m 2 ) cutoff points for overweight nd obese re set t 25 nd 3, respectively (17,19). In children nd dolescents, Overweight is defined s BMI (kg/m 2 ) the sex ge-specific 95th BMI percentile, nd t risk for overweight s 85th BMI <95th percentile (2 22). In children nd dolescents, we focused on overweight becuse ntionl estimtes of the prevlence of t risk for overweight hve not been mde vilble for ll wves of NHANES. Helth-cre costs ttributble to obesity nd overweight. Medicl costs ssocited with overweight nd obesity my involve direct nd indirect costs (13). Direct medicl costs my include preventive, dignostic, nd tretment services relted to obesity. Indirect costs relte to morbidity nd mortlity. Morbidity costs re defined s the vlue of income lost from decresed productivity, restricted ctivity, bsenteeism, nd bed dys. Mortlity costs re the vlue of future income lost by premture deth. Note tht our projections only provide estimtes of the overll direct medicl costs. We chose not to estimte the indirect costs becuse of the lrger uncertinty nd the need for more dt. In ddition, we focused on dults in our cost projections becuse of the bsence of published estimtes on helth-cre costs ttributble to obesity for children or dolescents. Min originl dtbses used for projections NHANES. The NHANES comprises series of cross-sectionl, ntionlly representtive exmintion surveys conducted since the 197s including NHANES I ( ), II ( ), nd III ( ). Beginning in 1999, NHANES becme continuous survey. Dt on weight nd height re collected through direct physicl exmintion in mobile exmintion center (14). Most recently, the NHANES dt collected in were mde vilble. Previous nlyses show little increse in the prevlence of obesity nd overweight between NHANES I nd II, but prevlence hs been stedily incresing since NHANES II (1,3,23). Medicl Expenditure Pnel Survey nd Ntionl Helth Expenditure Accounts. Recently published studies tht estimte obesityrelted helth-cre costs using the Medicl Expenditure Pnel Survey (MEPS) dt (1,11) provide bse for our projections of future helth-cre costs ttributble to overweight nd obesity. The MEPS is set of lrge-scle ntionwide surveys of fmilies nd individuls, their medicl providers (primrily doctors, hospitls, nd phrmcies), nd employers cross the United Sttes, which is designed to support studies of helth-cre use nd expenditures (24,25). The survey begn in 1996 nd collects dt on the specific helth services tht s use, how frequently they use them, the cost of these services, nd how they re pid for, s well s dt on the cost, scope, nd helth insurnce coverge. Ntionl Helth Expenditure Account (NHEA) provides ggregte mesures of helth-cre expenditures in the United Sttes by type of service delivered (hospitl cre, physicin services, nursing home cre, etc.) nd source of funding for those services (privte helth insurnce, Medicre, Medicid, out-of-pocket spending, etc.). The Office of the Actury in the Centers for Medicre nd Medicid Services nnully produces projections of helth-cre spending for ctegories within the NHEA for the next decde (26). Sttisticl nlysis Projection of future overweight nd obesity trends. We estimted the verge nnul increse in the prevlence of overweight nd obesity nd predicted the future prevlence mong US dults nd children ssuming the trends would be similr to those of the pst three decdes. Most of the pst prevlence estimtes bsed on NHANES dt used in our nlysis were bsed on previously published estimtes, ll of which were bsed on nlyses done with considertion of survey design effects nd smpling weights (1,3,23). Additionl estimtes were obtined only when necessry (e.g., prevlence nd shift in BMI distributions) nd were lso clculted tking design effects nd smple weights into ccount. For exmple, such nlyses were conducted using the survey-relted commends in STATA Relese 9. (Stt, College Sttion, TX), nd the relevnt strt, primry smpling units, nd smpling weight vribles were used. We fit liner regression models with the prevlence s the dependent vrible nd the survey time s the predictors for different sociodemogrphic groups. The β coefficients indicte the verge nnul increses in the prevlence. The models fit the dt well in ech sociodemogrphic strtum, nd explined 6 1% (i.e., R 2 ) of the vrince in the prevlence. The mjority (~9%) of the models hd n R 2 >.9. Bsed on the findings, we then projected the future sitution for the yers of 21, 22, nd 23 s well s when the prevlence would rech the lndmrk levels (e.g., 8 nd 1%). In ddition, we clculted prediction intervls bsed on the s.e. of the predicted prevlence (27). Further, bsed on previously observed BMI distribution shifts between 1976 nd 24 we predicted future BMI distributions mong dults ged 2 nd then projected the men BMI nd prevlence bsed on these projected BMI distributions. We creted weighted percentiles for ech wve nd estimted men BMI within ech percentile. Subsequently, the cumultive reltive frequency (proportion) ws compred between wves nd the yerly shift in men BMI for ech percentile ws estimted using ordinry lest squres liner regression models with survey midperiod s the predictor for men BMI in ech percentile. This yerly shift ws then pplied to the NHANES popultion to project future BMI distributions. Projection of obesity-relted helth-cre costs. We mke two sets of projections bsed on our projected prevlence nd two recently published estimtes of per cpit excess helth-cre costs ttributble to obesity nd overweight mong US dults (1,11). Thorpe et l. used the MEPS nd found tht in 21 the verge helth-cre costs for the obese group ws $1,69 higher thn for the norml weight group, nd for the overweight (25 BMI < 3) group, ws higher by $34 (refs. 1,11). Finkelstein et l. estimted tht the nnul excess helth-cre costs ttributble to obesity were $732 per person in 1998, nd $247 for overweight (1). We estimted per cpit excess helth-cre costs due to obesity nd overweight for ech yer from 2 to 23, ssuming tht the excess costs grow t the sme rte s per cpit personl helth-cre costs in the NHEA, which hve been projected to 216 (ref. 28). We pplied the verge nnul growth rte of per cpit personl helth costs between 25 nd 216, 6.%, to the rest of the study period. To clculte totl helth-cre costs ttributble to obesity nd overweight for ll US dults, we pplied our projected prevlence to the popultion projection provided by the Census Bureu. We lso expressed these costs s percentge of the totl personl helth-cre costs in the NHEA, nd s percentge of totl helth-cre costs estimte from MEPS. Totl personl helth-cre costs in the NHEA re projected to grow t 6.9% from 216 to 23, the sme s the nnulized growth rte from 25 to 216 projected. Totl helth-cre expenditures from MEPS re vilble for We ssume tht these estimtes grow t the sme rte s the NHEA personl helth-cre costs. Note tht primrily becuse of coverge differences (e.g., smple popultion included) tht MEPS estimtes of totl helth-cre expenditures re lower thn those of the NHEA (29). The projected costs were lso converted to 2, dollrs ssuming 3% nnulized increse in the gross domestic product defltor VOLUME 16 NUMBER 1 OCTOBER 28

3 Tble 1 Averge nnul increse in prevlence of obesity nd overweight mong US dults nd children nd future projections bsed on NHANES to Age Gender Ethnicity Adults, 2 yers Overweight nd obesity (BMI 25 kg/m 2 ) Obesity (BMI 3 kg/m 2 ) Children, 6 11 yers Overweight (BMI 95th percentile) Men nd women Current ( ) Averge nnul increse (percentge points) (OLS) Prevlence projections: prevlence (%) nd projection intervl Rte (β) s.e. R All ( ) 78.5 ( ) 86.3 ( ) Men All ( ) 8.1 ( ) 86.6 ( ) Women All * ( ) 78.1 ( ) 87.2 ( ) Men Non-Hispnic ( ) 81.3 ( ) 87.8 ( ) Non-Hispnic * ( ) 68.5 ( ) 72.7 ( ) ( ) 85.2 ( ) 91.1 ( ) Women Non-Hispnic * ( ) 73.7 ( ) 82.3 ( ) Non-Hispnic * ( ) 9. (77.5 1) 96.9 (81.2 1) * ( ) 81.9 ( ) 86.7 ( ) Men nd All ( ) 44.2 ( ) 51.1 ( ) women Men All * ( ) 4.7 ( ) 47.6 ( ) Women All * ( ) 5.3 ( ) 58. ( ) Men Women Boys nd girls Non-Hispnic Non-Hispnic ( ) 41.5 ( ) 48.8 ( ) ( ) 42.7 ( ) 49.1 ( ) ( ) 39. ( ) 44.8 ( ) Non-Hispnic ( ) 41.7 ( ) 47.9 ( ) Non-Hispnic ( ) 66.9 ( ) 75.6 ( ) ( ) 5.1 ( ) 55.8 ( ) All ( ) 25. ( ) 29.7 ( ) Boys All ( ) 25.7 ( ) 3.7 ( ) Girls All ( ) 23.8 ( ) 27.9 ( ) Boys Non-Hispnic ( ) 23.7 ( ) 27.7 ( ) Non-Hispnic ( ) 25.8 ( ) 3.2 ( ) ( ) 35.7 ( ) 41.1 ( ) Girls Non-Hispnic ( ) 21.1 ( ) 25.1 ( ) Non-Hispnic ( ) 33.9 ( ) 39.5 ( ) * ( ) 23.4 ( ) 26.5 ( ) Tble 1 Continued on next pge obesity VOLUME 16 NUMBER 1 OCTOBER

4 Tble 1 Averge nnul increse in prevlence of obesity nd overweight mong US dults nd children nd future projections bsed on NHANES to (Continued) Age Gender Ethnicity Adolescents, yers Overweight (BMI 95th percentile) Current ( ) Averge nnul increse (percentge points) (OLS) Prevlence projections: prevlence (%) nd projection intervl Rte (β) s.e. R Boys nd All ( ) 26. ( ) 31. ( ) girls Boys All ( ) 26.4 ( ) 31.6 ( ) Girls All ( ) 23.3 ( ) 27.8 ( ) Boys Non-Hispnic ( ) 25.2 ( ) 3.5 ( ) Non-Hispnic ( ) 27.4 ( ) 32.8 ( ) ( ) 31.2 ( ) 37.1 ( ) Girls Non-Hispnic ( ) 2.8 ( ) 24.7 ( ) Non-Hispnic ( ) 35.3 ( ) 41.1 ( ) * ( ) 24. ( ) 27.6 ( ) Ordinry lest squres (OLS) liner regression models included prevlence s function of time s the independent vrible. The β coefficients cn be interpreted s the nnul chnge in prevlence. Note tht time periods for ech Ntionl Helth nd Nutrition Exmintion Study (NHANES) survey ( ) were represented by the mid-point of the survey period. For, only NHANES dt collected between 1988 nd 24 were dequte nd used in our projection. The projections were conducted ssuming no popultion distribution chnges regrding ge, sex, nd ethnicity fter 24. Prediction intervls were estimted fter estimting the predicted projection s.e. for ech projection yer. 95% confidence intervls were estimted s predicted prevlence ± 1.96 s.e. Bsed on the 2 CDC Growth Chrts. *P >.5 for null hypothesis tht β = ; ll the others P <.5. All nlyses were conducted using STATA Relese 9.. We hve considered other projection methods, but felt the presented pproches re pproprite nd provide strightforwrd nd interpretble results. Our liner models hd excellent fit s shown by the high R 2 vlues. Our projected results bsed on yer-specific prevlence (liner models) nd those bsed on BMI distribution re consistent. Even though prediction intervls were estimted in our study, literl prediction of the future scenrio in the United Sttes would be ffected by mny possible uncertinties including policy-, environmentl-, nd behviorl chnges tht would require mny more ssumptions nd more complex models thn were pplied here. Rther we imed to show in reltively strightforwrd mnner wht the future would be if the trends observed in the pst continue. RESULTS Projected prevlence of overweight nd obesity from 21 to 23 On verge, the prevlence of overweight nd obesity hs incresed stedily mong ll US popultion groups over the pst two to three decdes (P <.5), but some noticeble differences exist in the verge nnul increse (percentge point) cross sex-, ge-, nd ethnic groups (Tble 1 nd Figure 1). In generl, US dults sw fster increse in obesity thn the increse in overweight in children nd dolescents (.68 vs..46 nd.49, respectively); women hd fster increse thn men (.91 vs..65 for combined prevlence of overweight nd obesity). Girls hd slower increse in overweight thn boys (.41 vs..49 in children nd.45 vs..53 in dolescents). White men nd women hd the highest increse rte in the combined prevlence, compred with Africn s nd s (MAs), within gender. Regrding obesity, Africn- women hd the highest prevlence nd rte % Overweight nd obesity (BMI 25) Obesity (BMI 3) 1 Observed Projected Observed Projected Yer All Men Women b % of increse overll; nd in men, the prevlence ws similr, but men hd the highest increse rte. The ptterns in children nd dolescents were complex. Our projection models show tht by the yer 23, ~9% (86.3%) of ll dults would become overweight or obese nd 51.1% of them would be obese. Blck women (combined prevlence 96.9%) nd MA men (91.1%) would be the groups most ffected. In children nd dolescents, prevlence of overweight would increse 1.6-fold (to ~3%) by 23. MA young boys nd dolescent girls would hve the highest prevlence (both 41.1%), level tht would be 1 percentge points higher thn the ntionl verge. Further, the prevlence Yer 27 All Men Women Figure 1 Prevlence of obesity nd overweight mong US dults: Observed during nd projected. The projected prevlence presented here re those bsed on our liner regression models VOLUME 16 NUMBER 1 OCTOBER 28

5 Tble 2 Future projections: time when the prevlence of overweight or obesity mong US dults will rech 8, 85, 9, nd 1% nd prevlence of overweight (BMI 95th percentile b ) mong US children will rech 3, 4, nd 5% Gender Ethnicity Yer when the prevlence will rech 8% 9% 1% US dults Overweight nd obesity (BMI 25 kg/m 2 ) All All Men All Women All Men Non-Hispnic Non-Hispnic Women Non-Hispnic Non-Hispnic Obesity (BMI 3 kg/m 2 ) All All Men All Women All Men Non-Hispnic Non-Hispnic Women Non-Hispnic Non-Hispnic Yer when the prevlence will rech US children nd dolescents 3% 4% 5% Children, 6 11 yers All All Overweight b Boys All Girls All Boys Non-Hispnic Non-Hispnic Girls Non-Hispnic Non-Hispnic Adolescents, yers All All Boys All Overweight b Girls All Boys Non-Hispnic Non-Hispnic Girls Non-Hispnic Non-Hispnic The projections were mde using liner regression models bsed on Ntionl Helth nd Nutrition Exmintion Study dt collected between 1974 nd 24, nd ssumed no popultion distribution chnges regrding ge, sex, nd ethnicity fter 24. b Bsed on the 95th BMI percentiles in the 2 CDC Growth Chrt. obesity VOLUME 16 NUMBER 1 OCTOBER

6 b Men BMI (kg/m 2 ) c BMI difference BMI (kg/m 2 ) NHANES II NHANES III NHANES Cumultive proportion/percentile NHANES II NHANES III NHANES Cumultive proportion/percentile Figure 2 Shifts in BMI distribution mong dults between 1976 nd 24: NHANES II ( ), III ( ), nd () Kernel density plot of BMI. (b) Cumultive proportion distribution of BMI. (c) Men BMI difference within percentile, m d: ordinry lest squres (OLS) estimte of verge yerly shift. in MA dolescents will increse by twofold nd mong Africn- teens, by 1.8-fold, the lrgest increses. Furthermore, our findings from compring BMI distributions between NHANES II ( ) nd suggest gret BMI increse in the upper prt of the distribution. Note tht previous study hs exmined the shift up to NHANES III ( ) (ref. 3). This is clerly shown in the incresing re under the upper til, the widening of the BMI men differences in the upper percentiles nd n upwrd sloping m d plot (Figure 2). Assuming these trends will persist, we projected the future BMI distributions. Bsed on these projections, men BMI b BMI or % Tble 3 Projected direct helth-cre costs, in billions of dollrs, ttributble to overweight nd obesity for US dults: 2 23 Overweight nd obesity (BMI 25 kg/m 2 ) Billions ($) Projection A Billions % % of $2, NHEA MEPS Billions ($) Obesity (BMI 3 kg/m 2 ) Billions of $2, % NHEA % MEPS $ $ $ $ $ $ $ $ Projection B b BMI (kg/m 2 ) NHANES $ $ $ $ $ $ $ $ MEPS, Medicl Expenditure Pnel Survey; NHEA, Ntionl Helth Expenditure Account. Projection bsed on per cpit excess helth-cre costs ttributble to obesity nd overweight estimted by Thorpe et l. (11). b Projection bsed on per cpit excess helth-cre costs ttributble to obesity nd overweight estimted by Finkelstein et l. (1). will increse linerly from 27.9 in to 31.2 in 23; nd by 23, 78.9% of dults will be overweight or obese, while 49.9% will be obese (Figure 3). In generl, these results re consistent with our liner regression model bsed projections Obesity prevlence (%) Overweight prevlence (%) % Overweight % Obesity BMI Men BMI Figure 3 Current BMI distribution nd projected distributions for the yers of 21, 22, nd 23. () BMI Kernel density plots. (b) Men BMI, obesity, nd overweight prevlence VOLUME 16 NUMBER 1 OCTOBER 28

7 Time course to rrive t 1% prevlence In ~15 yers, by the yer 222, 8% of dults would be overweight or obese; nd the prevlence would rech 1% in ~4 yers (by the yer 248) (Tble 2 nd Figure 1). For women, the time course to rech 1% prevlence is <3 yers (by 234). Hlf of US children nd dolescents overll will become overweight round the yer 27, but this level will be reched mong girls nd MA boys by 25. The projected obesity-relted direct helth-cre costs Totl helth-cre costs ttributble to obesity nd overweight will be more thn doubled every decde (Tble 3). By 23, helth-cre costs ttributble to obesity nd overweight could rnge from $86 to $956 billion, which would ccount for % of totl helth-cre costs, or for 1 in every 6 dollrs spent on helth cre. Becuse of the ssumptions we mde nd the limittions of the vilble dt, these figures re likely n underestimtion of the true impct. DISCUSSION Our nlyses, bsed on ntionlly representtive dt collected over the pst three decdes nd the ssumptions of similr future increse rte nd helth costs s observed in the pst, clerly show n lrming picture of the future obesity epidemic nd relted chllenges. Our projections show tht if the trends continue, in only 15 yers 8% of ll dults will be overweight or obese. The potentil for ll dults to become overweight or obese is relity, especilly for subgroups such s women where the current prevlence is lredy 78%. At the current rte of increse it will tke <3 yers for ll women to become overweight or obese. Our projections lso indicte tht the direct helth-cre costs ttributble to obesity nd overweight will be more thn doubled every decde. By 23, costs could rnge from 86.7 to billion US dollrs, ccounting for 1 in every 6 dollrs spent on helth cre. This is likely to be gross underestimte, s we ssumed tht the obesity-relted per cpit helth-cre costs grow t the sme rte s the per cpit totl helth-cre costs, when some evidence suggests tht the gp between per cpitl spending between obese nd norml weight individuls in fct is growing significntly lrger over time (11). For exmple, possible future chnges such s erlier onset of obesity nd complictions in younger dults nd vilbility of more costly helth-cre services my substntilly increse relted helth-cre costs. Although some my question the ssumption tht the observed trends in the pst 3 yers will continue nd some ongoing nd future policy nd progrm chnges my ffect the future trends, bsed on the current literture, there re few signs tht the increse will slow down. It is possible tht the increse my slow down when the future prevlence reches high level or due to emerging effective interventions. On the other hnd, there re continuing chnges in the society (e.g., contextul environmentl fctors) nd people s lifestyles tht my put growing proportion of the popultion t incresed risk for obesity. In fct, the increse observed mong women over the pst two decdes nd the recent ctch up of prevlence in women provide some evidence to support this concern. The potentil role of socil norms in promoting obesity development ws suggested by n nlysis of weight gin within socil networks (31). Incresing proportions of the popultion who re obese my result in chnges in ttitudes bout wht constitutes helthy body weight. The environmentl nd behviorl forces fueling the obesity epidemic re unlikely to be modified overnight, nd even effective prevention progrms my tke yers to show significnt impct. A cler impliction of our findings is tht the ntionl objectives specified in Helthy People 21 relted to obesity cnnot be met, except for the limittions of this study (e.g., the ssumptions mde). These objectives need be ressessed nd refrmed to be more relistic nd to provide the motivtion for pced but deliberte effort to stbilize nd then reverse the trends of obesity increse. A growing body of reserch iming t better understnding of the underlying cuses of the growing obesity epidemic suggests tht complex fctors operting interctively t multiple levels (e.g., individul, community/school, society, nd interntionl) re importnt contributors to this ntionl public helth crisis (7,32 34). For problem s pervsive nd serious s the obesity epidemic we hve observed t present nd projected for the future in the United Sttes, it is likely tht brod, comprehensive pproches re needed to ddress it. As rticulted by the World Helth Orgniztion for the globl sitution (35) nd by the Institute of Medicine with respect to childhood obesity in the United Sttes (36), drmtic nd effective popultion-bsed progrms nd relted policies need to be developed nd implemented to ddress the epidemic. But until recently, there were few truly multifctoril prevention inititives, the focus being insted on chnging individul behviors. More recently, there hs been incresing recognition of the mjor role tht the obesogenic environment plys in perpetuting the epidemic (37 39). Wht is needed now re cretive inititives to ctully effect environmentl chnges, nd this will require strong nd sustined collbortion mong the public nd privte sectors, eductors, food producers, urbn plnners, trnsporttion experts, prents, nd the generl public. The ntion s helth-cre system should be prepred to fce the rising burden of obesity-relted helth consequences, by providing more relevnt trining to medicl nd helth-cre professionls nd developing the needed infrstructures. Our study hs certin limittions. As noted previously, our projections re bsed on number of ssumptions, some of which re simplified scenrios. Future policy-, environmentlnd behviorl chnges my prove these ssumptions wrong. Future obesity rtes my not proceed linerly s the epidemic continues, while our projections essentilly ssume tht the environment will continue to worsen t pst rtes. Other potentilly relevnt fctors include segment of the popultion tht my be geneticlly protected from obesity or who my mintin lower risk of developing obesity through persistent helthy lifestyle behviors. The forces of the US obesity epidemic my not ffect such individuls. In ddition, our projected obesityrelted medicl costs were probbly underestimtes considering tht more obese people will be severely obese in the future; thus, helth-cre costs per obese person will be higher. Future obesity-relted helth costs will lso be higher due to the obesity VOLUME 16 NUMBER 1 OCTOBER

8 vilbility of more expensive relted services. Creful explortion of these complex fctors ws beyond the scope of this study nd the informtion provided by currently vilble dt. It is our hope tht the predicted grim future of the obesity epidemic will not turn into the ctul scenrio in the United Sttes or ny other countries. Projections for popultion subgroups tht lredy hve prevlence of 8%, e.g., women, suggest tht it is indeed possible for the hypotheticl levels estimted here to become relity. Although some individuls my be less prone, geneticlly, to gin excess weight, we might indeed be pproching environmentl nd behviorl conditions such tht few re exempt. We hope tht the results presented here will provide evidence of the severity of the obesity epidemic, of its impcts on the society, the lessons tht other countries cn lern from the United Sttes, nd ultimtely, of the recognition tht we, collectively, re the only ones who cn prove these projections wrong. Hence, we offer these nlyses to pose the questions wht obesity prevlence will be cceptble going forwrd? Wht gols will we set, nd how will we ttin these gols? Acknowledgments The study ws supported in prt by the US Deprtment of Agriculture ( ) nd the Ntionl Institutes of Helth (NIDDK R1 DK63383 nd NICHD 1R3HD5673). We thnk Dr Zhng for his ssistnce by providing some of the dt used in our nlysis. Y.W. contributed to conceptuliztion, sttisticl nlysis, literture review, interprettion of results, nd write-up of the mnuscript. M.A.B. nd L.L. contributed to dt mngement nd sttisticl nlysis, interprettion of results, nd write-up prt of the mnuscript. B.C contributed to interprettion of results nd revision of the mnuscript. S.K.K ssisted in dt nlysis, interprettion of results, nd revision of the mnuscript. DISCLOSURE The uthors declred no conflict of interest. 28 The Obesity Society REFERENCES 1. Wng Y, Beydoun MA. 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