According to Longman Dictionary, painfully means :
1- very – used to emphasize a bad or harmful quality that someone or something has
2- needing a lot of effort
This is the text:
"...and his college basketball days are far enough behind him that his chest muscles have turned into saggy manboobs that were painfully obvious through his freebie dot-com polo shirts." - Little Brother by Cory Doctorow
Is it "very obvious to find out" or "it needs a lot effort to find it out"?