i just remember the ending of the yaoi manga so i remember that the seme was skinny and the uke said that his sex drive was too much for the uke and so the seme gained weight and his sex drive was gone and days passed and the uke was feeling lonely because all they did now was cuddle so he told his seme to start working out and lose weight and he did and his sex drive came back

Tsukiatte Agete mo Ii n Dakara ne. That scenario was in the last few pages, though the seme's weight loss was a pretty major theme throughout.