Eachpersontookthetesttwiceovertwodaysandbeforehandreceivedeitheraninjectionofghrelin,ahungerhormonethatisreleasedbythestomach,orashotofsalineasacontrol.Theghrelinjabmadevolunteersravenousforonetotwohours.
Unsurprisingly,thehungryvolunteersbidconsistentlymoreforfoodandlessforinedibleitemsthanthevolunteerswhohadthesalinejab.Thehungrypeoplewerewillingtospendanaverageof$2.09forfoodand$1.32forotherobjects,butonsalinebidonly$1.82forfoodand$1.58fortheinedibleitems.
Thescientiststracedthebehaviourtoincreasedactivityinabrainregioncalledtheventromedialprefrontalcortex,whichisinvolvedinmotivationandreward.
"Ghrelinseemstoincreasetheamountyouarewillingtopayforfoodthroughthisareaofthebrain.Wethinkthisiswhyyouassigngreatervaluetothefoodwhenyouarehungry,"Daghersaid.TheresearchwaspresentedattheSocietyforNeurosciencemeetinginWashingtonDC.
Butthestudyfoundthatpeopledidnotsimplypaymoreforfoodstheyliked.Instead,thehigherbidswereforthehigh-caloriejunkfoods.
"Whenyouarehungryyouassignwaytoomuchvaluetocaloriesandsowaytoolittletohealthandotherthings,"Daghersaid.
Dagherbelievesthatsimplybeingawareofthewaythebrainworkscouldhelppeopleovercometheurgetobuyjunkfoodwhentheyarehungry."Wehavethisintrinsicvaluesystembutwecanoverrideitwithourminds,"hesaid.
Thefindingssupportevidencethatshowsskippingmealstoloseweightcanbecounterproductive."Ifyoumissmeals,youtendtogainweightbecauseyougethungrierandeatcaloricallydensefoods,"Daghersaid.
