I think someone who is 80kg and fat is stronger than someone who is 50kg and all muscle.
Someone who is overweight at 80kg is likely more powerful than a 50kg muscleman.
この場合、次のような言い方ができますよ。
ーI think someone who is 80kg and fat is stronger than someone who is 50kg and all muscle.
「筋肉だらけの50キロの人より太った80キロの人の方が強いと思う」
ーSomeone who is overweight at 80kg is likely more powerful than a 50kg muscleman.
「太り過ぎの80キロの人は、おそらく筋肉隆々の50キロの人よりもっと強いだろう」
ご参考まで！
カナダ 
