For me this cake is too fat? Я не уверен что можно использовать здесь слово fat.

Можно сказать fatty

Только не for me, а TO me.

I double-checked myself regarding "for me" with a native speaker

high-calorie - это вовсе не "жирный". Сахар тоже high-calorie

точно, Вы правы.
Оставлю перевод в комментариях.
This cake is too high-calorie for me ( высококалорийный)

too much fat/butter = rich FOR me

Uly, I read somewhere on a form that if something is difficult to do, I say "FOR me It's hard to do sth", while if an object or a surface I touch feels hard, I should say "It's hard TO me." It looks like I didn't catch something, could you please clarify it.

TO is used for impressions, FOR is used to express how something suits or doesn’t suit you personally: This book is too long for me. This cake is too rich for me. This movie is too racy for children. Smoking is bad for you.

Got it, thanks.

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