I thought I would look better if I lost weight, but it wasn't necessarily the case.
I though my looks would improve if I lost weight, but it didn't happen.
ーI thought I would look better if I lost weight, but it wasn't necessarily the case.
「痩せたらかっこよくなると思ったのに、そうとは限らなかったよ。」
look better で「格好よくなる」
lose weight で「痩せる・体重が減る」
not necessarily the case で「そうとは限らない」
ーI though my looks would improve if I lost weight, but it didn't happen.
「痩せたら見た目がよくなると思ったのに、よくならなかった。」
looks で「外見・見た目」
ご参考まで！
カナダ 
