"Ten mężczyzna jest gruby."

Translation: This man is fat.

[AnCatDubh]

‘The’? Not ‘this’?

[mihxal]

Both answers should be accepted.

[Azcatral]

Also fat as in "this milk is 5% fat"?

[Kami12087]

No. What your said is "To mleko ma 5% tłuszczu".

"Gruby" means "fat" (about a person) or "thick" (e.g. a book).

[Arnoldpitt]

gruby sounds like brudy