LONDON—Here’sanewwarningfromhealthexperts：Sittingisdeadly.Scientistsareincreasinglywarningthatsittingforlongperiods—evenifyoualsoexerciseregularly—couldbebadforyourhealth.Anditdoesn’tmatterwherethe

　　LONDON—Here’sanewwarningfromhealthexperts：Sittingisdeadly.

　　Scientistsareincreasinglywarningthatsittingforlongperiods—evenifyoualsoexerciseregularly—couldbebadforyourhealth.Anditdoesn’tmatterwherethesittingtakesplace—attheoffice，atschool，inthecarorbeforeacomputerorTV—justtheoverallnumberofhoursitoccurs.Severalstudiessuggestpeoplewhospendmostoftheirdayssittingaremorelikelytobefat，haveaheartattackorevendie.

　　InaneditorialpublishedthisweekintheBritishJournalofSportsMedicine，ElinEkblom­BakoftheSwedishSchoolofSportandHealthSciencessuggestedthatauthoritiesrethinkhowtheydefinephysicalactivitytohighlightthedangersofsitting.

　　Whilehealthofficialshaveissuedguidelinesrecommendingminimumamountsofphysicalactivity，theyhaven’tsuggestedpeopletrytolimithowmuchtimetheyspendinaseatedposition.

　　“Afterfourhoursofsitting，thebodystartstosendharmfulsignals，”saidEkblom­Bak.Sheexplainedthatgenesregulating(调节)theamountofglucose(葡萄糖)andfatinthebodystarttoshutdown.

　　Evenforpeoplewhoexercise，spendinglongperiodsoftimesittingatadeskisstillharmful.TimArmstrong，aphysicalactivityexpertattheWorldHealthOrganization，saidpeoplewhoexerciseeveryday—butstillspendalotoftimesitting—mightgetmorebenefitifthatexercisewasspreadacrosstheday，ratherthaninasinglebout(一回)．

　　Still，inastudypublishedin2009thattrackedmorethan17000Canadiansforaboutadozenyears，researchersfoundpeoplewhosatmorehadahigherdeathrisk，whetherornottheyexercised.

　　“Wedon’thaveenoughevidenceyettosayhowmuchsittingisbad，”saidPeterKatzmarzykofthePenningtonBiomedicalResearchCenterinBatonRouge，wholedtheCanadianstudy.“Butitseemsthemoreyoucangetupandinterruptthissedentarybehavior，thebetter.”

　　FiguresfromaU．S.surveyin2003­2004foundAmericansspendmorethanhalftheirtimesitting，fromworkingattheirdeskstosittingincars.

　　Expertssaidmoreresearchisneededtofigureoutjusthowmuchsittingisdangerous，andwhatmightbepossibletooffsetthoseeffects.

　　“Peopleshouldkeepexercisingbecauset