Translation:The woman is heavy.
Truth is truth. Plus you don't know who's talking. Could be a baby. Could be a horse.
Can this be used the same way as in English? Or would it sound weird compared to whatever the korean word for "fat" is?
It's not considered rude to be quite direct. For example, saying "Wow, you're fat." Isn't rude in South Korea (Or East Asia in general) It's as if someone went up to you and said "Wow, you have eyes!" You already know your eyes are that color. They're just expressing surprise and stating facts- not trying to be rude.
I think this thread is the one that I get the most notifications on in Korean. Hopefully in real life, women speaking Korean or any of the other 7 000 languages know well enough to lose faith in people that care about them that tell them not to be upset by (unnecessary) comments about whether they are sufficiently pleasing or amusing to others. The same applies to men, although men tend to be evaluated as an individual person for a start.