He is whining every now+then following me from room to room,always seems hungry?

my 5 yr male staffy is restless ?? he is whining every now+then also following me from room to room, he always seems hungry ?? he is on a good brand of dry dog food i got frm local pet shop and has been for the last yr or 2 , also has plenty of toys + things ??? im jst a little frustrated why this has happend only recently ? :(