[单选题]Exerciseisoneofthefewfactorswithapositiveroleinlong-termmaintenanceofbodyweight.Unfortunately,thatmessagehasnotgottenthroughtotheaverageAmerican,whowouldrathertryswitchingto“light”beerandlow-caloriebreadthanincreasephysicalexertion.TheCentersforDiseaseControl,forexample,foundthatfewerthanone-fourthofoverweightadultswhoweretryingtoshedpoundssaidtheywerecombiningexercisewiththeirdiet.Inrejectingexercise,somepeoplemaybediscouragedtoomuchbycaloric-expenditurecharts:forexample,onewouldhavetobrisklywalkthreemilesjusttoworkoffthe275caloriesinonedeliciousDanishpastry.Evenexerciseprofessionalsconcedehalfapointhere.“Exercisebyitselfisaverytoughwaytoloseweight,”saysYorkOnnen,programdirectorofthePresident’sCouncilonPhysicalFitnessandSports.Still,exercise’ssupportingroleinweightreductionisvital.AstudyattheBostonUniversityMedicalCenterofoverweightpoliceofficersandotherpublicemployeesconfirmedthatthosewhodietedwithoutexerciseregainedalmostalltheiroldweight,whilethosewhoworkedexerciseintotheirdailyroutinemaintainedtheirnewweight.Ifyouhavebeensedentaryanddecidetostartwalkingonemileaday,theaddedexercisecouldburnanextra100caloriesdaily.Inayear’stime,assumingnoincreaseinfoodintake,youcouldlosetenpounds.Byincreasingthedistanceofyourwalksgraduallyandmakingotherdietaryadjustments,youmayloseevenmoreweight.7.Somepeopledislikeexercisebecause________.
