Losing too much weight on marathon training!

hey,,,im a guy,, and for starters,,if u can have see on runners in sprint racing and ones in marathonn,,there seems to b a difference between their physicall apppearnce,,sprinters have muscle still but long runnerss marathonn dudes,,dont,,the reason is,,da sprint training probabbly makes dem reach the HIIT factor,,which is kinda traing which makes u losee alot of fat,,other dan dat in marathon da person keeps on goin and goin and everybody is really skinnnyy,,the thing is,,ure muscle is losin aswell instead of fat,,the body is taking energy by breakin down the muslce,,ure glucose level is probably down too,,ure probably not having enuf fat or proteins,,u shud check on ure daily intake on vitamins if u are takin any,,u shud,,waisayu,,i am not sure abt the science of it all,,but im sure wat i just said to u abt da muscle breakk down is wats goin onn,,u need protein nd atleast some fat ,,the boddy does need an amount of fat,,soo u need to find a veggie with high content of protein available at ure local store,,u need to google dat veggie and seems if its available,,just dont overexert ureself