when i got my girl spayed she packed on the pounds but i know most dont i think it may slow some dogs matabalisums down, but its nto from not getting enough exersice cuz she gose for a run in a like 90 acre feild every night for half a hour so i dont know but get your boy spayed i thought the prong collar was gonna kill my dog when my parents got it for my dog but i was only little i cried when they put it on him we dont have it anymore but now i use a harness