i dunno abotu the whole mcdonalds thing. you will gain weight but it proabably wont be muscle. try takign a supplement liek 1-AD and use it right. you will naturally get hungrier and if u eat good foods high in protien yoru will eventualy get soemthing. Also dotn neglect yoru legs, they helped me gain soem weight. and just so u know, the suggested value for 20 year old who works otu can consume up to 3,500 calories a day and soemtimes more.