Comme dit Mickaël, de ces jours, on dit "fitness", mais si on veut éviter les anglicismes, on dirait plutôt "culture physique".

"fitness" is commonly used in french, so if you say : "J'aime le fitness", french people clearly understand you. There's no exact equivalent in french, because we already use the word "fitness" to talk about the sport to stay fit and healthy. But if you really want to use a french word, you could translate this with "gym" which is a short word for "gymnastique" but "gymnastique" has the same meaning of the english word "gymnastics". I hope that I answered your question.

We use fitness ! The same way we use jogging and shopping, they're called anglicismes.